which one to buy? mx-1 or m-80

I am in the market for an amp to power my yamaha ns-1000m speakers. And though many say tube amp - I'm limiting my search to solid state.

There are both an m-80 and an mx-1 available right now - the mx-1 is about $150 more than the m-80. I've read a few posts that suggested the m-80 might be better even at the same price and other posts that suggest the mx-1 is the best.

On another note (probably for another thread) I am currently powering the speakers with an old Quad 405 II that I've had for ages. It sounds pretty good to me just as it is - but I've seen so many threads suggesting the latest mods to that amp. Would I be better off spending my cash on modding the 405 or buying one of the yamaha amps and keeping the 405 as it is?