I was in a similar situation about a year-year and a half ago and eventually went with the 17-55 f2.8 and the 70-200 f/4 IS, which for me are a great kit. The IS isn't absolutely necessary on the tele, but I found it helps quite a lot (price tag vs shaky hands argument). I absolutely love the IQ on both lenses and haven't had any cause to complain...well...apart from carrying the weight for a whole day, it is a noticeable increase on the kit lens + cheapo zoom (I had the 70-300 non-L). The 17-55 does suffer a bit with night photography, your 50mm prime would probably be the best there, but even so it is definitely much better than the previous kit lens and if you use a tripod should allow for some great shots.