I am currently running a 1050 with a old Parasound 1200IIa (205 wpc) driving my NHT VT1.4 mains. I am trying to position myself to replace the 1050 with a separate pre-pro and am looking for am amp that would primarily handle the center and surround speaker loads. Currently, I am running NHT SuperZeros for the rear center and side surrounds and a NHT VS1.4 for the front center. Both amps are right in the middle of the recommended power range for these speakers.

From a spec perspective the Parasound appears to be slightly quieter (< .03 THD vs < .05) and slightly more powerful 85wpc albeit in a 5 channel mode. From a price perspective the used 855 is about half the price of a new 7075. I am not sure that I would ever use the two additional channels of the 7075 except as emergency backup in the event my 1200 failed.

Given this, what are anyone's thoughts on a 7075 versus a used Parasound 855. Do solid state amps age? Also from a WAF would I expect to hear any immediate difference by replacing the 1050's amps with either (again just for the surrounds)?

Power wise, I don't think you'll have an issue with a 7075. I currently use SuperZeros for surround duty and used to have a 7075. It was more than adequate. With all NHT's though, the more power you can supply the better as they are fairly low sensitivity speakers due to their sealed design. I had Classic 3's for a while (fronts and center) and additional headroom seemed to make a difference. I don't recall the looks of the 855, but the 7075 has a pretty compact profile for an amp. I used to have some amps that were older and never noticed the sound 'degrading' due to their age, so I don't think that's a worry. Guess it boils down to appearance and price.