Okay, so I have been pondering a new camera body and was curious of a few things....First, I don't have a whole lot of cash to go crazy with holidays coming up...Second, it will continue to be a Canon body (sorry Mike, no Nikon here). My main questions are these:

1) Will I gain much by upgrading from the XSi (450d) body to say the T2i, 50d, or 60d? I generally shoot the glasses and ebay stuff and occasional sports events like my daughter's softball or the drag races

2) What is the biggest benefit of the full frame sensor vs. the aps-c that seems to be in like...everything Canon has except the really pricey cameras?

3) Would it just make more sense to pick up a couple of lenses and keep my current body? Looking at 3 lenses: ef-s 60mm macro, 70-200mm f/4 non is (budgetary reasons), and 50mm 1.4 ef...any insight will be greatly appreciated...

1) There's little reason to jump from an XSi to a 50 or 60D. The next jump would be a 7D or a Ti2 depending on your budget. The 40D seemed to be the last one in that line to really deliver for the price.

2) Full frame will only be appreciated on the wide lenses. I found little difference on my 70-200 for example, but the 24 was night an day. If you don't do much landscape or really wide shots, there's not much point. Although the larger sensor will give you fatter sensor pixels, so noise will be less etc. On my 5D II, I shoot ISO1600 standard, while I keep my 40D at ISO400 max. Of course there's also more pixels, so when resized the noise appears less. Apples and oranges, but you get the idea.

3) Yes, new lenses will always make sense. The XSi is a fine camera, so given the choice pick up some more lenses. Of the ones you listed, I'd aim for the 70-200 off the bat, since that will be a great lens to use for many things. Then maybe the 50/1.4 and skip the 60mm macro and spend a bit more for at least the 100mm macro (old one, not the new L version w/IS). 60mm just won't give you the same effects.

I imagine reading this thread is what it feels like for a newbie to Oakley trying to figure out what we're talking about...

That whooshed right over my head.

1) As a fellow XSi user, I will let you know that if I had the money to upgrade, I would shoot for the 7D. Just like Mann said, I'm not convinced the performance you'd gain beyond the XSi with a T2i or 60D is worth the price. In my mind, the only worthy selling point of those models over an XSi is video, and I've already got a point and shoot that I can use for video in the meantime.

2) I've never shot on anything larger than the APS-C, but it has one advantage that is useful when shooting something like your daughter's games. The 1.6x crop factor effectively gives you longer lenses. This is obviously a disadvantage if you're trying to do group shots or something that requires a wider angle. For field sports though, I've been satisfied using the crop factor to my advantage.

3) I also coupled the XSi with the 70-200mm and have used it at baseball and football games with success. I have a 50mm, but it is the 1.8, which could save you a bit more cash. While the 1.4 certainly would give better image quality, I never have regrets about the 1.8. It literally is like a toy. It's small, inexpensive, and I don't expect too much from it. In some cases, that's exactly what I need.

I've been told by several photographers, some of them friends, some professionals, "Put good glass in front of any body."

Cool. I thank you for the replies Dann and Bob...

The t2i seems to share a lot with the 7d according to the specs and dpreview.com as for bodies. My money seems to be better suited towards the lenses. I have pondered on lenses for a while now, and it actually cost me in the end. I was going to buy the 70-200mm f/4 a couple years ago and they were about $200 cheaper than now...Now to find someone parting with clean lenses...LOL Thanks again guys. Made my decision(s) easier. I can always use the lenses on new bodies down the road..as long as canon sticks with this mount which is probably a given...