I guess it depends of "how serious" you want to get involved in photography and if you really need some features found in the expensive models.
From this comparison:
http://www.dpreview.com/products/com...ts=canon_eos7d you can see that the 3 models are pretty close im many aspects but the price difference between them is striking: $4-500 for T3i, $1000-1200 for D60 and $1500+ for 7D.
You need to consider if you really need the 19 AF points of 70D or 9AF is enough. Also, the continuous drive (is 3 FPS enough or you need better?) Maximum shutter speed: is 1/4000 enough or you think you'll need 1/8000? There are also some other aspects - you'll need to have a close look and to decide in the end how much you want to pay.
To sum it up: The Rebel 3Ti gives a very good ratio of price/performance. Given the low price, you might very well go for the T3i and replace it in one year or two with a better model.
But that's only my opinion
