Marantz av7005 vs av8801 vs Theta Casablanca

One question along the line with replacing the fuses. Should I plug the amplifiers into my Furman power conditioner? It's the 20a version. Thanks 

One of the things I really like about the av8801 and av8802 is that Marantz put in a very large power supply for this processor, so the sound will be very full and have a lot of muscle in the bass and midbass.  

I definitely agree with you on the full sound, I'm just watching Netflix movies right now and I can tell a difference between the av7005 and av8801 in the low frequency content. It just seems smoother than the av7005. I plan to use the av8801 at least through the weekend, providing I can get Audyssey to set up correctly, then I'll try out the Theta. 

One other thing I would note is between the av7005 and av8801 streaming movies sound much less like an mp3. The av7005 would sound very digital at times. 

Sorry, that message posted before I was done.  I don’t know much about av8801 configuration quirks.  Probably best just to read the manual and try to work from there.  There are definitely some processors that will not do bass management (i.e. subwoofer output) for 2-channel music.  My old Krell HTS had that quirk.  However, the new Krell S1200 and Bryston processors will enable sub for 2 channel music.  If you are using an analog source (like turntable or external DAC), the Marantz could be acting as a pass through preamp, in which it does no conversion to digital for bass management.

Good choice working with an active crossover (like I mentioned before).  I have worked with Ashley pro equipment.  I’m assume you are looking at something like the XR-1001 crossover.  The Ashley stuff has a tube like bloom to the sound.  I believe part of the reason is that Ashley’s internal power supply runs at the bare edge limit of the op amps (+/-18V).   If you want something with a flatter more neutral response, look at a used Rane AC22 crossover.  Rane power supply runs at a more conservative +/-15V.

if you are willing to spend the money, the Bryston 10B is probably the best.  Fully discrete Class A analog circuits with big linear power supply.  Make sure you know which version.  Some versions have RCA, some XLR.  The Bryston will have the most resolution/transparency compared to Rane or Ashley.

if you can get the Emotiva and Marantz to sound good, you may not feel the need to bixamp.

There is nothing that you can do easily with the Emotiva other than a fuse upgrade.  I had XPA-1 Gen 1 in my system.  Currently, I am running with XPR-1 and XPA-1L amps.  Both of these amp versions use two fuses (such as 2 x 4A for the XPAx1L).   I found that my Emotiva amps sounded the best with one Isoclean fuse and one Furutech fuse.  It was an excellent balance of clarity and warmth.  I found that running two Isoclean was just too warm/slow.  Running with two Furutech was too thin/lean.  I am using a really fast high resolution Krell processor (not warm at all). In your situation, it might be that two Furutech would sound best because the Marantz is so warm/slow.  The type of interconnects and speaker cable and power cables could also affect the sound.

fuses are used to help “tune” your system to get further towards the type of sound you want.  I just gave you my two preferred fuses.  You can start however you like.  If you do get fuses, make sure to burn in before making any decisions.  100 hours for the Isoclean.  With Furutech, you need about 240 hours before it calms down (because of the rhodium).