glass generally lasts longer than a body, and will affect IQ more than the body. So, you're dumping most of your money on a soon to be discontinued body (that is still priced relatively high) and not spending much on glass, which would last you for the next body you buy.
The 30D has one advantage, imho, over the XTi -- build. People debate the ISO performance, the true advantage of the sensor clean (on the XTi), or the extra two MP.
So, if you buy a 30D, you get $200 on glass -- not much you can do there at all.
If you buy an XTi, you get $600 on glass. Not a lot, but a decent amount for 1 ok lens and something cheap -- like a 50 1.8. For intermediate zooms, think Tamron -- not Canon -- at this price point ($400 range, for a lot more lens). You can get an affordable f2.8 zoom.
If you really want the tele instead of the wide, then the 70-200L or 70-300 Canons would be good. But, personally, I couldn't imagine having a body without a lens in the critical 17/24-50/70 range, particularly on a 1.6 body.
And don't ignore Nikon (I shoot Canon -- have used/owned XT, XTi for backups, 30D, 5D, 1DIII, so I know the range, but still think you can't ignore the other side). A D80 and Tamron 28-75 is about $25 over the $1200 price point.
DSLRs are expensive. Lens are expensive. But, glass is very important.