The 7d will not give you much more IQ then the rebel you have. Additionally its large and heavy.
Are you suggesting a Rebel XT is as good as a 7D?
I am saying that the difference in IQ might not be worth the extra weight and cost.
By the way, I have a rebel t2i. My brother in-law has a 7d. We just spent a few days together on vacation shooting street shots and nature shots. This was my first hands on experience with a 7d. I "played" with it quite allot as we exchanged cameras now and then. I was quite surprised to discover - that it was quite impossible to see any difference AT ALL between the t2i and the 7d as far as IQ! This is comparing a $700 camera to a $1,700 camera!
Of course the 7d focuses faster, is much more rugged, has a larger viewfinder, and shoots much faster fps.
Ironically - I have a close friend with a 60d. Once again - surprise - the 60d in my opinion - has BETTER IQ then both the 7d and the t2i. (Its a newer camera) even though "on paper" its the same 18mp sensor.