Anthem A5 enough to drive B&W 804D3 fronts and HTM1D3 Center?

I would think that the Parasound Halo A31 would be a better power amp than the Anthem A5. 

Re the hiss you heard from 2 feet away IMO there might have been something else in the signal path somewhere in your audio chain eg your preamp, kind of interconnects (single-ended or XLR), speaker cables, power cables, AC power line or AC power product, front end source component(s) that are the cause......again it's possible but I don't know for sure and can't confirm. But usually the noise floor is determined by your amp, but who knows something else might have contributed. 

What at preamp are you using? What front end source component (digital or analog eg turntable) do you have? What kind of cables are you using? it's very likely that your AC power line product or your main AC power line in your home might be the source of the hiss that you heard from 2 feet away. Is your main AC line off your wall outlet grounded and do you have a dedicated line? What kind of AC power product are you currently using? 

But again I've never personally heard the Parasound Halo A31 before but my buddy and many other people I know have and they said it is a great amp especially for the money. And the SNR of 112db on your Parasound A31 is a good number and in theory the noise floor should have been pretty low. 

The power output rating of the Anthem A5 at 180 wpc @ 8 ohms will be enough power to drive your B&W 804 D3. These are pretty efficient speakers and aren't hard to drive assuming you have good quality clean amplification and not using some AV receiver. 
But I would think that the Parasound Halo A31 would be a better amp than the Anthem A5. The Halo A31 is highly regarded and received high recommendations from various different hifi reviewers or magazines / publications. You can never go wrong with this amp. 

Another good amplifier option for your B&W 804 D3 will be the Classe Sigma Amp2 stereo power amp or the Sigma Amp5 give-channel amp or the higher end series Classe Delta CA-2300 stereo amp or the CA-5300 five-channel amp. Even the lower priced Rotel RMB-1585 five-channel power amp will have great synergy with your B&W as well. 

Thanks so much for the detailed reply.  You asked a couple of questions that I'll answer.

On the hiss, I've tried everything to get rid of it.  I've (a) used a cheater plug; (b) swapped for very expensive Audioquest MacKenzie RCA interconnects; (c) bought a Furman elite power conditioner; (d) unplugged the coax entirely; (e) unplugged all components except the amp (and it still hisses); and (f) lowered the gain on the amp (this brought the hiss from 2 ft down to 10 inches, but the negative side effects on speaker volume aren't worth it).  I spoke with Parasound about it, and they believe that it's a characteristic of the amp floor.  Others on other forums also have had these issues with the amp.

I'm using a Denon x7200wa as a preamp, though the end goal is to get a Marantz 8805 or an Anthem once HDMI 2.1 boards are installed.  My source is Tidal a (very high-end) home theater PC.  It's connected to the Denon with a digital coax cable for audio (and HDMI for video).  The digital coax is a generic cable from Amazon.  Everything is plugged into a Furman Elite 15 pfi power conditioner.

To be fair, the noise floor is pretty low in the sense that I absolutely cannot hear it from where I'm sitting in the room.  I sit between 8 and 9 feet away, and the noise is absolutely inaudible after 2 feet.  And even then, it's inaudible over 1 foot except at a height right in line with the tweeters.  So really, I may be letting the perfect get in the way of the good here.

As to the Parasound, I agree that it's highly regarded.  I picked it because the first 7 or 8 watts are pure class A, which is unheard of at its price for an amplifier with 250w RMS all channels.  I also got a good deal on it.  But that deal came with a price -- it's basically unreturnable because it was a special order.  The store is making an exception and will let me exchange it for an Anthem MCA 525 (for an additional $600), an Anthem A5 (for an additional $1100), or the Rotel RMB-1585 (even trade).  I also could go for any other Anthem, Rotel, Parasound, or Mark Levinson product, but there were no other similar choices in the price category that I'm looking at (and they aren't a Classe dealer).

With those choices, I don't want the MCA 525 because I've read a number of posts (and verified with Anthem support) that it sometimes sends pops to speakers when it turns on and off because they removed some sort of relay.  I don't want the Rotel because I previously auditioned a Rotel RB-1590 (the big 350w 2 channel one) and found it inferior to Parasound in sound quality -- I suspect that the 5 channel one isn't as good.  

That leaves the Anthem A5 or just sticking with the Parasound.  I'm on the fence.  I don't want to lose sound quality, but I'd like to get rid of the hiss for peace of mind.  It seems rather silly when you stop to think about it, though -- I hear the hiss only when I get very close to the speaker, yet I hear the sound quality and use overall amperage/wattage of the amp every day.

I really appreciate your thoughts.

Well.....if you like the way your Parasound A31 amp sounds you should stick with it and don't worry about hissing and it isn't audible from your listening position anyways....I wouldn't worry about it. 
A better AC power line product will help lower the noise floor of your system. I would highly recommend either Audioquest Niagara series (1000, 5000, 7000) or any Shunyata Research power products. But your AC wall outlet needs to be grounded and I highly suggest to hire electrician to get a dedicated grounded line for your hifi setup. 
It will make a world of a difference. 

I myself use two Audioquest Niagara 7000 products in my dedicated home theater room since I have multiple high powered monoblock amps and a multi-channel amp in there. I have a pair of Classe Delta CAM-600 monoblock amps driving my main front speakers (B&W 800 D3); Classe CAM-300 monoblock amp (single) for my center speaker (B&W HTML1 D3); Classe CA-5300 five-channel amp for my surround speakers (B&W 804 D3 & 805 D3). I'm doing 7.1 setup. My AV preamp surround processor is Classe SSP 800. My only AV source is the Oppo UDP-205 4K UHD bluray player and a Sony 4K OLED TV (85"). My sub is a JL Audio Gotham.
All these gears but the sub are plugged into my two Audioquest Niagara 7000. The JL Audio Gotham sub is plugged directly to the wall outlet.

In my dedicated stereo setup in a separated dedicated listening room I have the Shunyata Research Hydra Typhon QR which consists of Hydra Triton & Hydra Typhon. I have two pairs of Dan D'Agostino Monentum M400 monoblock amps in bi-amp mode driving a pair of Magico M6 speakers. I use an Audio Research Reference 10 linestage analog stereo preamp. My digital front end consists of the DCS Vivldi full four stacks (Vivaldi master clock, Vivaldi upsampler, Vivaldi DAC, Vivaldi CD/SACD transport). 
My analog front end rigs consist of the following : Kronos Pro turntable with a dedicated Kronos Pro stand, 12" Black Beauty tonearm, Air Tight PC-1 Supreme mc cartridge, class A linear PSU, Audio Research Reference 10 phonostage preamp. 
All these gears are plugged into the Shunyata Research Triton & Typhon.  

As for power amp choice, since you have B&W 804 D3 speakers I would highly recommend getting Classe amplifiers. Classe and B&W 800 series D3 speakers are meant to be paired together. They have perfect sonic synergy together. Especially the 800 series D3 these speakers were designed and tuned and voiced using Classe gears. 
Either the Classe Sigma Amp5 / Sigma Amp2 amps or the higher end series Classe Delta series amps will sound phenomenal on your B&W 804 D3. The Delta series amplifiers are much more expensive than the entry level Sigma series amps but are better than the Sigma series amps and will be a noticeable improvements sonically from your Parasound A31. Try to find the nearest Classe dealer in your area to demo the amps. FYI, all Classe Delta series products were discontinued last year and can be had at discounts these days. 
And these Classe Delta series amps exhibit astonishingly low noise floor. The noise floor is almost non-existent. Deadly quiet. The soundstage emerges from a very dark black background. Great amps. Especially the CAM-600 monoblock amps, like the ones I have in my dedicated home theater room. But these Classe CAM-600 monoblock amps will be way overkill for your B&W 804 D3. I think the Classe CA-2300 stereo amp will be perfect or even the much lower priced Classe Sigma series amps will be great choice for your speakers. 

You mentioned that you are currently using a Denon receiver as your preamp processor and thinking to upgrade to the new Marantz AV8805. While the Marantz AV8805 processor would perform great for surrounds or home theater (movies) and will be a step up from your current Denon receiver but its stereo performance for stereo music playbacks or when used as a stereo preamp aren't on the same level of sonic qualities as high end dedicated stereo preamps. What are your priority? Do you use your setup for both stereo music and home theater (surround sound movies) or just mainly home theater? If you value stereo music playbacks I would highly recommend the Classe Sigma SSP preamp surround processor. This unit is optimized for stereo performance for music playbacks and its performance as a stereo preamp is superb and sounded more like a high end analog stereo preamp than an AV preamp processor. Its multi-channel of surround sound performances for movies is also excellent. 

Preamp or preamp processor plays important role in achieving overall good sound for both your musical and movie sound effect reproductions. 
The new Marantz AV8805 is great for home theater (surround sound movies) however. 

I also have the Triton and Typhon combo in my tube horn set up.  
I upgraded my outlets to porter ports which made also made a difference. 

While the Triton/Typhon are great for  lowering noise floor and removing grunge, it won't fix noise generated by the amp.   I have 107DB speakers and can pick up a very small amount of 60hz hum generated from the 60 watt Nagra VPA amps.   This would most likely never be heard from 85 to 90db speakers  that the Nagras were designed for in the early 2000s. 

It's noticeable at 2 ft, but not at my 12 ft listening position.  I of course tried all the usual tricks like cheater plugs, and thought that the ground terminals on the Trident would help, but the noise always remained.   I I've had other amps that were dead quiet, but so far the Nagra had the best sound quality overall, so I live with the fact that there is audible very low level hum at 2 ft that i can't hear from my listening position.


If Parasound is correct and the hiss  is the noise floor of the amps, then it's unlikely you will be able to get rid of it with external power filtering.