For your budget and room size, consider the Tekton Electron. It is not the last word in refinement or imaging, but does a good job tonally and dynamically and should meet what you are looking for.
If you stretch your budget a bit, there is a pair of Legacy Classic HD for sale currently on US Audiomart for $3500. I am a big fan of Legacy, though I am not as enthusiastic about the Studio HD as some others here. The monitor of theirs to get is Calibre, but it is not likely to be found in your budget. As others have mentioned, with your amp I would get something with a sensitivity above 90 to 92 db.