Ideas for amp to run woofers on a bi-amp system.

Bryston 14B SST2 perhaps?

Actually quite a few used Bryston SST, SST2 models within your budget. Solid performers, and hold their resale, with exceptional reliability. The cubed series are better, but within your budget, possibly not.

Class D, someone recently put me onto Nord Three SE 1ET400A MKII Dual Mono Stereo Amp. Apparently an exceptional application of class D technology from the reports I have been reading.

It makes sense to go used, especially if it's a temporary solution, to recoup your investment.

Older, high current, very stable into low impedances, and sounds like the real thing (fast and highly controlled Bass reproduction/excellent square-wave response), describes the first (and subsequent) Hafler TransNova amps. ie: (https://www.hafler.com/pdf/history-of-the-transnova.pdf)                                                                                                 Early model test results: (https://www.stereophile.com/content/hafler-transnova-9500-power-amplifier-measurements)                                                                                                                                                                  Not too salty, either: (https://reverb.com/item/2032061-hafler-9505-trans-nova-power-amp-black)                                                                                                                                     or (depending on your wattage requirement): https://www.hifishark.com/search?q=hafler+9303

I’m interested in what you end up going with, please post the animal you purchase when you do?

Crown XLS 2502