Hey palmer, your experience of knowing how both the 5Ts and 6Ts sound in your room should prove helpful to others torn about which tower to get. Did you also upgrade from the 5C to the 6C, or did you just go straight for the 6 from the get-go? At any rate, seems like you have a pretty killer system!
Hope the link above takes you to the thread of 5T vs 6T. Accurate description from Jason: 5T's are great system with a subwoofer. blkhks makes a great point on the size of the 6T and needing floor space.
For my situation, I was looking to upgrade my existing old, pieced together "4.0" system by adding a center channel, the 6C. I could not afford the whole set of 'sixers' at one time.
However, while purchasing the 6C, the local guru on call showed me an open box of 5T's, and I was able to swing the deal and try them out knowing I had 30 days to upgrade.
My plan had always been to go with 6's for towers, center, and rears with no subwoofer, but the sound of the 5T's made me take a serious look into Aperion sub's.
It's a tough decision, but my final answer, is to stick with an all 6er 5.0 system (2-6T's, 6C, 2-6B's). The deciding factor, for me, besides having the room for the 6T's, came down to the comparison of sound on John Bonham's percussion on Physical Graffiti. His base drum is not the lowest, but does sound the 'fullest' with the 6T's. The added bonus has been the wider range of mid's.