As a disclosure, not a professional here, but over the past 8 months or so, I too upgraded to from the entry level Canon DSLR. I spent a ton of time going back and forth on Nikon or Canon. Ultimately I chose a Canon 60D. ( I know depending on who you ask, the 60D could be great or the worse camera ever made) For my part it has been an incredible upgrade. I had actually bought the 7D and upon finding out it was CF returned it. Bad experience with a corrupt CF card. I have since picked up low light lenses, either from Adorama, KEH or even EBAy and have been very lucky on quality. Currently, I have a 50 1.4 (Canon) and a 70-200 Sigma 2.8 which stays on the camera alot more than I thought it would.
With the budget listed, I know the 60D offers a really clean higher ISO range than the entry level. Looking at my receipts, the body and the Sigma 2.8 ended up costing me about 500 less than 2000.