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

Well we dont carry solid state amps only tube and this is just meant as a temporary fix until we expand out product line. As a result I would like to keep the cost at below 3 to 4K.

My speakers are Ascendo Model Ms which are tri-ampable. Im just using jumpers currently and the sound is very good, but I can just tell that more power is in order if I continue with the current configuration. 

The speakers are listed as 6 ohm nominal, but in numerous contacts with Ascendo they havent responded to my questions regarding the impedance curve. I would guess that they go down to roughly 4 ohms and this, in my mind, is a bit low for most tube amps. Definitely too low for OTLs which are among my favorite amps on the market.

To be honest when reviewing new products, I find the feedback from users more useable initially than that from manufacturers or distributors.  

Crown XLS-1502! 525 wpc at 4ohms! 8.6 lbs. Fan cooled. $449.00 with free shipping from various online sellers. Sure, it's class D - but so what! If I needed a new production amp for bass duties in my system this would be my first choice! The XLS1502 has a built-in active crossover so it can be used only for bass frequencies in a bi-amp system! Or conversely for mids/highs!

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?