I want to buy a DSLR but for now my budget is a little tight.?

I'm trying to decide between some of the entry level DSLRs. I need something above point and shoot cameras to capture some moments I've been missing. I've done some research on the Canon XSi, Pentax K-x, and Nikon D3100. I believe those are in the same price range and have some similar characteristics. My decision will be based on shutter speed, good quality with low light, frames per second, built quality, and lens selection. If you have any other suggestions please let me know.