Sounds like a good plan to me.I've been waiting for ages for a review like this to come out. Pretty sold on them after listening to the 607s. I'll be partnering with a Denon AVR-4400 and I'm debating whether I can afford the 603s. Whilst my house is slightly too small now i move around fairly regularly with work. The plan I think is to get 606s and the centre first (keeping my current rears or even getting 607s) and then in time upgrade to the 603s and put the 606s at the rear.
Thanks very much for a great review and if you see any holes in the plan please let me know.