reefergal wrote in post #4170843
I did not think about having to get new glass along with a new camera. New glass was not in the budget.
This is the single most important factor here and you haven't mentioned what lenses you have now.
If you have a lot invested in digital-only/EF-S lenses, you would probably be best to buy a 30D or 40D (respectively $800-$1000US used/new, and $1300 new).
If you have all or mostly full-frame-capable lenses in your existing kit, a 5D may be ideal for your purposes. (I am not up on the going prices for them, new & used.)
If your budget is tight, you could consider buying used from a reputable place like keh.com, B&H or Adorama. There seem to be some very good deals on 30D and 5D right now. 40Ds are so new a model that they are essentially unavailable used at present.
Going from the XTi, you are losing a modest amount of image resolution with a 30D (10MP to 8MP). However, the ergonomics and overall functionality of the camera, plus it's general durability, are a step up.
Going to a 40D would give you resolution equal to the XTi, with some additional IQ tweaks thrown in for good measure, plus the same and a few more ergonomic, functionality and durability upgrades as a 30D would.
The 5D would give you a modest resolution increase, 10MP to 12MP, and has similar overall ergonomics, functionality and durability to the 30D. But, as a full frame camera, the 5D offers the highest potential image quality, least crowded sensor, and best control over depth of field. These are all important considerations for wedding and portrait work. On the other hand, the camera's technology is older, although certainly still quite capable.
Personally, I just bought a second 30D and vert/batt grip a couple weeks ago, and have relegated my 10D w/grip to backup camera status. I will probably replace the 30Ds with 40Ds sometime next year, but am not in any rush to do so. The 40D's improved viewfinder and AF are probably the biggest considerations for me. On the other hand, the 30D cost me about $500 less, a good one was easily found, I'm quite familiar with using it and I avoided any possible new product "Beta" glitches with it (the 40D appears to be free of these, except for some isolated examples, so far... unlike the 1D Mk III). I just might also add a 5D w/grip sometime soon, but don't have a real need at present.
But, my shooting needs are much different from yours, so this is really not intended as a buying guide, except to say that I don't think you need to be concerned about buying a lightly used camera - if that helps stretch your budget - and to point out that there are some great deals on "last year's models" right now, both new and used. That's true even of the 5D, which is only rumored for replacement at this point in time. If you decide on a 30D, you'd better hurry since existing stock of them will probably sell out pretty fast.