Under 1500$ Solid State Amp for Usher Be-718

I recently picked up a new Harman Kardon HK990 amp for $1,500, and I can't recommend it enough. It easily pushes my Mirage OMD-28s, and they have never sounded better. Instruments sound infinitely more real. Imaging is fantastic, sounds is warm but not too much. I listen to music a ton more than I used to, because of this amp.

The room correction software, and bass management are invaluable!
Mot

Odyssey Audio Khartago.

Deciding to go for Musical Fidelity M3i or M6i, is there any
major difference between sound quality of both amps, as M6i is
900$ more.

Any suggestions will be welcomed

That sounds like a great combo (I have my Ushers running offa MF 3.2 int amp and really like the results.

If it were my choice, I would pikc the M3i and save a few bucks. It will drive the Ushers fine.