i want to get into photography and i have been researching all day lol

i have a sony cybershot 7.2mp but i was looking at the rebel xti's all day.

im planning on getting one that just comes with everything that i need to get started or should i wait and get the XSi?

i plan to use it on capturing paintball photos like this:
http://wichita-mayhem.com/index.php?showtopic=482

most of those were taken with my original camera i have now.

i just want some tips thats all. what lens would work best with this type of photography?

or will the lens that comes with the rebel work fine?

thanks