I think I made the decision to get Canon EF-S 55-250mm f/4-5.6 IS + Canon EF 50mm f/1.8 first. So I will end up paying around $360 for the first try! see if my skill is good enough to get the best out of those or not. It should be better than throwing $350 on one 50mm f/1.4 alone and I can get nothing out of damn good lens. :-)
You know that I like your idea, do you? ;P The thing is we'll never know how good the more expensive one is if we never try the cheaper one, right? You're the best ever!! You got tons of my great shots (because you took tons-tons-tons of photos.) 55555 I mean it, you're excellent.
Just went and tried both lenses [Canon EF-S 55-250mm f/4-5.6 IS + Canon EF 50mm f/1.8] I got a conclusion that the more expensive you pay, the better you will get. That made me sad :'( e.g. holding D90, shooting for a bit to get used to, the result I got is superb already, while holding XSi seemed to be great, but not near as good as D90 most of the time. I don't know how 50D will perform though.
Love 50mm f/1.4 haha, but if I decide to buy prime lens, 50mm f/1.8 probably is the one.