How about Powercore or UAD-1???
I own the MPX110, and have used the MPX550 as well.....never used the MPX1 though. The 110 is OK.....the 550 is actually quite good, I liked it alot more than the 110, and Im sure the MPX 1 would be another step up in quality from there. but seriously......how about PoCo or UAD-1???
Drammy has some nice EMT 140 plate samples somewhere around here, a good reason for the UAD-1, and not only do you get amazing reverb now with UAD-1, you get bloody LA2A and 1176LN!!!!!!!!!!!
And what about PoCo.....they have some cool stuff too, and now they got that ultra compact cool looking PoCo, but maybe expensive...
Good luck, hope I didnt confuse you with choices
Jase