Hi Luis,
Interesting I have the virtually the same set-up apart from the power amplifier.
Also, I had the Summit's and now have the Summit X. I did post a very high level comparison some time back (link below):
http://www.martinloganowners.com/~tdacquis/forum/showthread.php?t=10009&highlight=summit
To be honest, I think there is a very substantial difference. The panel is voiced very differently, the crossover is much better and the integration from panel to woofer is the most seamless that ML have so far produced.
I too had the same dilema - it was a fair amount to upgrade (really I wanted the CLX however that was not within budget), but after changing over I was extremely pleased with my decision. I would strongly recommend you demo a pair and see what you think.
As a side note, I am comtemplating changing my power amplifier to the ARC Ref 210 - I don't suppose you tried that when selecting your Ref110?
Feel free to ask any other questions / more details.
Thanks
Marc.