First Watt F4,5,6 or M2 for biamp

I am contemplating biamping my magnepan's mid/tweeter panel.

The F4,5,6 or M2 appear to have sufficient and similar power at 4 ohms, though I'm told there are subtle differences between them.

Is there any particular model that would excel in the mids and tweeters?

Presently, I don't have the time to devote to a build. I've heard that many forum members have legacy amps in their closets, having built many amps over the years and acquired a personal preference or experiencing system compatibility of one design over another.

From. what I understand, Mr Pass does not object to the sale of legacy amps as long as it is not a for profit business. enterprise, and sell them to fund their next First Watt project.

To that extent, if anyone wants to sell their legacy amp to a good home, please PM me. I promise to feed them a lot of signal and exercise them regularly. 😁

Because of shipping costs, I'm confined to amps living east of the Rockies or the West Coast.