Does Rega not make a suitable speaker ? Their speakers are generally well reviewed in the UK, and one would expect that they would work well with their own electronics. I haven't heard them .. just thought I'd suggest it.
My other thought is, must they be floorstanders ? If you could live with standmounts then I think you'd like Epos Es11 or M12. They produce a lot of deep bass for their size and will image better than most floorstanders at that price. Your price range is quite restrictive for QUALITY floorstanders. The Epos floorstanders are also very good, but probably over $1000 even used.
My other thought is, must they be floorstanders ? If you could live with standmounts then I think you'd like Epos Es11 or M12. They produce a lot of deep bass for their size and will image better than most floorstanders at that price. Your price range is quite restrictive for QUALITY floorstanders. The Epos floorstanders are also very good, but probably over $1000 even used.