One of the best amps I have heard driving the Abbys at any - yes, that's rght any - price range is the $800 SEP (single-ended Pentode) Almarro A205A. You can find them used here for ~$550.
I have heard this combination several times and it always blows me away with it's tonal purity. It simply sounds perfectly "right" in so many ways. The combination is a classic example of synergy where price really has no bearing.
For reference, I own the 7x more expensive Cain & Cain IM-Bens(opitonal brass ring) and optional Fosex T-900A supertweeter. Toss in the pair of C&C Bailey subwoofers and that is the best the Cain Company has to offer. I use a S&B TVC into Art Audio's best amp, the PX-25. I also have Welborne Labs DRD 300B monoblocks. (check the rest of my system here)
Yet, the first time I heard the A205A/Abby combo w/ Bailey sub I was overwhelmed with a deep sense of regret, buyer's remorse, whatever you want to call it. I am not kidding, this was magical. When you take price into consideration, it is a steal.
Of course, coming back home to my own system quickly reminded me of all the ways my setup outperformed the A205A/Abby combo. Specifically richness of tonality, scale, depth, etc, etc. But, every time I hear the combo again I am just as blown away as the first time.
Oddly, the A205A actually sounded as good or better with the Abbys than the AA PX-25, an Almarro A318A, and Audion Sterling ETSE EL-34 integrated that I own.
Please don't take this as a raving claim that the Abbys and A205A are the "greatest ever", no amp or speakers are. I'm just saying that the combo performs far beyond it's price range and what would be expected. And is definitely worth checking out.