Mirage M7si bass bump how to deal with it?/

It does not sound as bad as it looks and the speakers are very impressive I tried a marantz PM 8003 and that has pretty tight bass which helps Not sure if it is enough yet.

Agree with Onhwy61, or else get one of the digital room correction units and use it to shape the in-room response.

"04-17-15: Onhwy61
If you really want to alter the frequency curve, then use an parametric equalizer.
Onhwy61 (System | Threads | Answers | This Thread)"

Generally, I would prefer a different solution, but in your case, it may be the best way to go. Fooling with cables is no way to go about it. Something like a Behringer 24/96 digital eq should give you some good results. Since its digital, you can run it through a DAC for better SQ. The only other thing I can think of, besides an eq is to get a more powerful amp. The amps you list as tried are not the last word in power and control.

I owned these speakers M7si, and the M5si bigger version years back and they are nice sounding speakers for their time and price point. They are definitely NOT lacking bass regardless of placement or amplification. The upper bass is no doubt tipped up. Either deal with it or move on. They are no worth much money today anyway.
I sold my mint pair via Craigslist for $150 the pair and it took almost a month even at that price. Best of luck!!!

"They are definitely NOT lacking bass"

I believe the OP gets that.