Suggestions for an amp

I forgot to mention Musical Fidelity M5si stereo integrated amp ($2k) and the M6si stereo integrated amp ($3k). I highly recommend them for your Monitor Audio Silver 8 speakers. They both have USB assycrhinious DAC inputs that you can connect from your computer or NAS, etc.
These integrateds do not have a specific HT bypass input but you can use its aux analog audio input and set the volume at 80 for unity gain. 
Unity gain is basically the same as HT bypass mode. 

The Rotel RA-1592 stereo integrated amp that I also recommended to you earlier also does not have a specific HT bypass input, but you can use the aux analog audio input and set the volume at 80 and save the setting. Rotel will let you save your setting for unity gain or HT bypass input. So every time you select this input the volume on the Rotel will be disabled and fixed at 80.
So, for surround sound movies or HT use you simply control the volume and everything from your Yamaha receiver and the analog audio signal from your Yamaha receiver's front L/R channels pre-out will be routed directly to the power amplifier section of the Rotel RA-1592 integrated amp to drive your Monitor Audio Silver 8 front speakers. 

By the way, are you only doing stereo setup or surrounds (multi-channels)? 
If you're only doing stereo setup you don't even need the Yamaha receiver. You can sell it and get one of the stereo integrated amps recommended above. 
The Hegel stereo integrated that was recommended by soix is phenomenal. 

Thanks...would a Marantz PM8005 or 8006 do the trick. I've seen several reasonably priced

No, I wouldn’t get the Marantz PM8005 or 8006. Actually, the Hegel H160 stereo integrated amp that was suggested by soix earlier is currently for sale here on Audiogon for $1600. You should definitely grab it. Highly recommended! First, I didn’t realize if the Hegel H160 has digital inputs thus has built-in DAC and it has a dedicated HT bypass input as well.
Do not hesitate to buy it.

By the way, are you only doing stereo setup or multi-channels or surround setup?

As the other guys are alluding to, you probably want something more than the Marantz.  The Silver 8s drop to 3.5 Ohms in the midrange, which is not uncommon, but the P8006 puts out 70wpc and only rises to 100wpc into 4 Ohms indicating the power supply is probably not be up to driving your speakers fully.  It only weighs 26 pounds, so these limitations make sense.  By contrast, the Hegel weighs 42 pounds and puts out 150wpc into 8 Ohms and 250 into 4 that your Silver 8s could surely make good use of.  $1600 is a very nice deal on this amp, and you'll thank us once you hear it with your speakers.