Personally, I own an M-1.5t at the moment, and previously owned an M-400 "Cube", both from Carver, and I have always been pleased. I have heard stories of Adcom amplifiers going nuclear, and they take the speakers with them, but I can't vouch for that personally. If you scored a M-1.0t from GW, I would hold onto it. There is a man who can rebuild them, and make them more powerful.
You should go check out the website:
www.thecarversite.com Rich is a good guy who knows his stuff. Also, he was a Carver tech when Carver was making the M class gear, so he knows the stuff like the back of his hand.
As for a preamp, if you choose to go with a Carver pre, there are only two that come to mind: The 4000t, which is the final incarnation if the C-4000. Very high quality compared to the older C-4000's. The other one is the C-17 Vacuum Tube Preamplifier, but that one is worth quite a bit of money, so I would go with the first choice.
Outside of Carver, I would recommend the LS-3 from Audio Research. No tone controls, and the sound is identical to their tube gear. My dad has one, and it has an amazing sound. If I had the money right now, I would get one. For that matter, just about anything from Audio Research is great gear, and is worth the money.
Just my two cents though.