My affordable and all around excellent choice is Yamaha M4 (dittoing try1256). The B2 is a step above the M4 but hard to find and even harder to repair. With the wrong amp the NS1000s tend to be bass shy, with the right amp they are bass adequate and even bass good. The M4 gets better with a better preamp, I've often upgraded my system and the M4 sounds even better, like I bought a new amp..
The M4 also has a surge circuit when you turn it on which is extra protection for the NS1000s, the Adcoms, the B&Ks and many other amps don't. Hearing that chick 3 secs after turning the amp turns on is music to my ears. Highly recommended, every Yamaha household should have one!
I also like the Kenwood L07MII it outshines the M4 but does not embarrass it. The L07MII can also be hard to find and repair. The Kenwood L07CII preamp is as good or better then many of the Yamaha C (50,70, 80) preamps. The L07s show up from time to time at a decent price. I've tried a Kenwood M2A amp which at first I liked but after a while I found it too bright (the M4 is better), it really is good in the bass department if that is an issue.
I have also had good results Nakamichi PA 5AII. Some people love the Nakas and some find them too soft. But in a bright room (hardwood floors, lots of windows, etc) this amp is great, different from the M4 but not necessarily better.
Which brings me to what is often overlooked; placement and room treatment. A few inches closer to the ground or wall can improve bass response and sound quality as much as a different amp can. Likewise with room acoustics.
Your mileage might vary... Different strokes for different folks.
Michael