i forgot to reply to your fb message... Canon is like apple with its ipods in a sense. Every 6-8 months they come out with a new canon rebel that is supposidly to be better than the last hence why in the last 3 years you have seen the rebel xl, xs, xsi, t1, t1i, t2, bla bla bla. Invest in lenses and then when you decide to get serious or want to go pro, get your self a 5d Mk2 which is superb in low light
I know you want something thats good in low light and high ISO but if you invest in lenses with lower F-stops then you can shoot better at night. I just purchased a 85mm 1.4 yesterday which is amazing in low light, 1.2 is better but about $1000 difference for .2 of a difference.
You will get FAR more use out of a 10-20mm lense (because ive been dying for that lense for a while now as well lol) make sure you get the 10-20mm f 3.5 because you will be far happier with that instead of the f 4.0-5.6