An upgrade from what you have except for maybe the rears, is purely subjective as you appear to have a fairly good small speaker judging from the listed frequency responses, possibly a sub upgrade is all you really need. Something like the EP500 or EP600?
How thin do the speakers need to be, could they be on wall mounted style like the Axiom 'W' series? I would look at the M22 or the W22 and you could possibly use the new T2 to replace the in-ceiling speakers you presently have. For surrounds I would suggest the QS4 or QS8 if you have the room and with the QS speakers you may just find you won't need to use the inceilings for rear surrounds depending on the rooms seating arangement.
