Used amp recommendation

How about an Aragon 4004 to match your pre? There's one listed now at 1/2 your budget. I've had Aragon and Acurus is the past and was always pleased with them.

I'd suggest a solid (state) choice: Aragon 8008 BB or ST for around $1000 used.

Thank for great input.  I think I'll watch for an 8008 to come up.  

Audio Research 100.2. Owned one and it is a great amp. I know the Aragon amps well and Monitor Audio speakers. Not saying the Aragon aren't nice amps; worked at a shop years ago that sold them. For your budget and the speakers you have, I think you can do better. Parasound A23 or a used A21 would be a great amp as well and I have heard both on Monitor Audio's. The 100.2 is a killer amp and I probably should have kept mine. 

I am very happy with my Audio Research VT100 MK II.  There is one on Audiogon right now for $2,000.  It's a few dollars more than you are looking to spend, but it's a lovely amplifier.  ARC provides excellent maintenance service, though shipping to Minnesota for repair is a little expensive due to the weight and size.  Still, no regrets!  My previous amp was a Balanced Audio Technology VK-55.  I easily liked this amp as much or better than my ARC VT100 MK II, but I needed more power for my relatively inefficient speakers.  (In fact, I could still use more!)  Beware, going to the tubes may be a life altering experience!  Good Luck!