Forgive me if this has been asked a million times, but i'm indecisive and just need some help/advice 
I currently have an xti and just got a job being a photographer for a band. I went and shot them playing around in their garage over the weekend and my pics didn't come out too awful (thanks to the 50mm 1.8), but i've decided that I need to move on from the xti. ISO 1600 when I need a better shutter speed is just too poor in quality for my liking. I also have been trying to get some good shots of my sister playing basketball and it's difficult to get a high enough shutter speed in the gym to completely stop motion with my camera without the picture looking awful.
So here's my thing - I have been wanting a 5D for a while now, so I was planning on saving up for that. But I was told by others 'why would you get a 5D and spend that much when the 40D is good in low light also?"
I'm not a photography expert, i'm still learning and trying to get out there. I have been doing research and have found that the 5D seems to be better with noise than the 40D, but that the 40D is quite good too. The band wants me to shoot them at gigs (they mostly play at a bar here in town, which is quite dark inside) So, since most things I have found myself to be shooting lately call for high ISO, should I splurge and go for the 5D or go with something like the 40D? I just don't want to get a 40D and wish I had gotten a 5D.
thanks to anyone who has advice 
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