One thing to consider about the XT is the lack of AI Servo in anything but "sports mode." You really want AI Servo available in all modes including manual.
(AI Servo is what keeps a moving object in focus. This is needed a lot in sports.)
You might want to consider a used 20D which can be purchased for $900 or so for nice ones. (The price may fall some in a couple of months when the new replacement is announced.)
For baseball, you will want a long lens. If you can shoot in daylight most of the time and are on a budget, the new 70-300mm IS might work for you. It is a consumer lens but since you are on a budget and need reach.
I better lens that won't have as much reach would be the 70-200 f4L which is considered to be one of Canons better lenses.
For wide, you just mght pick a prime like the 35 f2 which is fast and sharp. However, it wnt be real wide on a 20D or an XT as the focal length is multiplied by 1.6. (That is good for you on the telephoto end but bad on the wide end.)
If you have a more moderate budget, I would suggest a 20D with grip, 70-200mm f4L, 1.4x TC, 17-40mm f4L, and a 50mm f1.8. This would get you a decent package for daylight and well lit night games plus have many other uses.
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