Lowend amp

And the definition for reasonably priced please…

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

What model B&w speakers do u have?

Krell has a New line up coming out very soon by June I was told.

AAvic  make  very good amps they are class D but of the highest order ,with technologies others Donot have and sound better then most class AB amps 

well worth checking out.you didnot mention your budget.

@audioman58 

He did...2k. and you're way out of his league.

The Parasound A23+ is in your price range. Damping factor >800. Class A/AB 160w@8ohms. 

Bryston 7BSSTs  are perfect for low bass control. I use them as my sub amps and love them. 800 watts into 1-4 ohms. Figure 4-5K for the mint ones with lots of warranty left. 

Adcom 565 mono's can be had at this price point

The Belles 350a has a damping factor of 3000 plus according to specs.

Krell KAV-300i, KAV-400XI

Damping factor has very little to do with bass output. My ksa 300s has a damping factor of 150 and has great bass. It's the size of the power supply that matters most. I doubt you will find anything with a power supply as large as those krell amps.

Speakers 800 matrix