Under 1500$ Solid State Amp for Usher Be-718

No one mention its own R1.5 ?
I have one driving my new BE20 - Sound so good that I bought 2nd one to use as monoblocks for the BE20 - and the 3rd one for my second system
BTW: I'm from tube world as I still own Cary 805C, Atma MA1. But these cannot drive the BE20

Used price is less than $1500 - built like a tank (89 lb)

I have the MF 3.2 and really like it with the Ushers. I think most of MF amps are within your budget.

I used to have the BE-718 mated with a Belles 150A Reference v2. Excellent match - precise, extended, dynamic with punchy bottom end, and smooth. Maybe not the best if you prefer a warmer, rosier sound (I've gone all tube). The Belles is pretty neutral, just a little on the warm side. McCormack DNA-1 is warmer and powerful as well and has very nice tone, but not precise enough for my taste in terms of imaging and soundstage. If I went back I would probably settle on one of the Bel Canto Ref amps. You can find a Ref500S for a couple hundred over your budget, or Ref150S for under $1k. I think the BE-718 would greatly benefit from the extra power though.

The Musical Fidelity M3i lists for $1500. I just bought one and I'm loving it.

I don't think Musical Fidelity is considered a warm sounding amp. At least this is my experience with their onlder gear. I have not heard their newer stuff.
The Usher amp does, in my opinion, have a very good sense of midrange warmth and does quite wel with the Usher 718 speakers.
Any of the amplifiers mentioned would work just fine with these speakers.