Lowend amp

2K

You could always look for another Krell, and I’ll throw in Hegel (very high damping factor) and Bryston (SST2 or cubed models) as a couple others worth looking at for tight bass.  Best of luck.  

Belles Reference 350a. There's a good one for sale on USAM for $1850.00 I think. I'm not the person selling it. Very high damping factor, and great reviews in all aspects.

Big B&Ws, I don’t think you can get anything that would equal the performance, sound and control of the KSA250 for $2,000. You would need a big high current amp. 

The Belles amp recommended by @roxy54 above actually looks interesting but I never heard it and don’t know how it matches with b&w. 
Another amp I would recommend and it’s super rare is a McCormack DNA500 but I’m not sure you can get it for $2,000