I recently decided to see if my old trusty Sony STR DA-9000ES would work well as a power amp.
When the STR-DA9000ES came out in 2004, it was considered a reference state of the art unit. The thing is built like a tank, and it's output topology was (and still is) ahead of the curve.
The problem with these types of units is that the processing and inputs can't keep up. When the unit came out, IEE 1394 (fire wire, or i-link), along with DVI, was the bleeding edge. As we all know, the processing and input setup has progressed right along, which means that reference units like these must rely on the analog input to stay current.
Last fall, I wound up getting a Sony STR-DA6400ES. On the whole, it's a excellent unit, with all the latest technology packed in (Network support, all the latest HD decodes, Auto Rate Control support with matching players, etc).
After using the 6400 for a few months, I rellay came to apprepripate it's sound quality. However, it's power out is 120W @ 8 ohms (2 channels), which drops accordingly with surround recordings/movies, etc.
So, I decided to try the 9000 as a 7 channel power amp. I also looked at the 7 channel Adcom, Sunfire, etc.
The take away is that the 9000 makes a outstanding amplifer. Mated with 6400, the sound is markely improved over the 6400 or the 9000 as stand alone units. The S-Master Pro technology employed by Sony (mated with a giant power supply transformer) is very hard to beat. It basically acts a zero feedback class A output (stepped digitally).
For those using a current generation receiver that could use some extra power, this is one way to get it.
