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

I own a pair of speakers that dip a bit in terms of impedance and I want experiment with using a solid state amp to run my  woofers in a bi-amp configuration. We do not carry a solid state electronics line currently. Speakers have 3 pairs of posts. I will be using the Zesto Bia amp to run the midrange and tweeters and need suggestions on a good amp/amps to run my woofers. Perhaps Class D? Any ideas on older high current amps that can be had used? Thank in advance!