Adam-
as a rule of thumb on non-IS lenses, to avoid camera shake you need to set a shutter spped roughly the inverse of the focal length because camera shake gets exaggerated by longer focal lengths. so if you are shooting with a 50mm lens, you need a shutter speed of either 1/45 or 1/60. on a 200mm lens, you need a shutter speed of 1/200 to avoid blur from camera shake. the canon IS system will get you 1-2 stops of correction. so at 200mm, you may be able to shoot at 1/90 or 1/125 with the IS engaged. however, your aperture at 200mm is likely to be f5.6 on that lens. at f5.6, 1/90, the sensor is not getting anywhere near enough light to properly expose the shot. I believe Rick shoots his IS 70-200 with a custom function that keeps the shutter speed at at least 1/90 or 1/60 (not sure which). and i believe he still shoots between ISO400 and 800 depending. the lens he is using is constant f2.8 which means it allows 4 times as much light to reach the sensor as the f5.6 will. at f5.6,there is simply not enough light entering the camera to properly expose the shot. shooting at ISO1600 will get you close, but i think the noise will be unbearable, considering you'd probably have to do some exposure compensation in post. all this is before you even evaluate how sharp that specific lens is wide open.
I still believe that primes are the way to go if you are on a budget. the only zoom option is the 70-200 IS (which Rick and jonny have). with a price tag rivalling that of a used car, it's not likely to be feasible. keep in mind that at 6mpix on the dreb, you have a good bit of cropping room. so even if you can't get all that close, with an 85/1.8 or the 100/f2, you can crop out a good bit and with some sharpening practice still have very very nice 8x10s.
Rick's points are well made. He has much more experience in this stuff than I do. He is no doubt right that the zooms are more versatile than primes. but as a cost/benefit analysis, i personally think you can get more for your $$ by going prime. for the price of the 70-200 IS, you can get the 50/1.8, the 85/1.8, the 100/f2 and the 135/f2. the consumer glass certainly doesn't hold its value as well as the L glass, but you can still resell it for a good price if its well cared for. each of those 4 primes I listed are constantly being bought and sold used at fredmiranda.com. the consumer glass typically gets about 65% of its new value or so, while the L glass will get 80-90% of its new value. that being said, if you buy used from a trusted seller, you are likely to be able to get close to all of your money back. it's pretty easy to experiment with a lens for a while and see what you think. there is no perfect lens (i think Rick would agree with that). so it's about finding what you think will be the best compromise for your $$. for me, I'm going with primes for concert shooting. overall, i have 2 primes (50, 1.4, 135/f2) and 2 zooms (24-70/f2.8 and 70-200/f4). of these, only the 70-200 is not usable for concerts.
and i totally agree with rick about the AF of the 10d/dreb, especially in low-light. I only use AF with the center pont and recompose or MF in low-light.
sorry for the long response, i hope it helps.