tytlnz,
I am running the about the same setup as gonk except I use the 7500 for my center channel and surrounds and two 2200's for my mains.
The reason I have set it up this way is so that my 7500 is turned off when listening to stereo music. It only comes on for SACD, DTS audio and DVD's.
For now I would use the 7500 for everything and when the time comes for 7.1 add a couple of 2200's and you will have one sweet system.