Canon Rebel xti and I was happy with my Sigma kit (18x50 & 55x200), that is until I put a borrowed Canon lens on that puppy. Images so crisp they remained so until 300% in ACR. I loved it.

I use a tripod 95% of the time and mainly do mountain landscape and the occasional critter that jumps out of the woods. I figure the range I had will work, maybe bump it up to 300mm, still using a pair of lenses. I should point out that my pockets aren't that deep so be gentle with your advice. Used doesn't hurt my ego.

So, will Tamaron glass give that crisp image or do I have to stick with Canon, or ??

Check photozone.de or slrgear.com

The tamron 17-50 f2.8 is very nice. I've only used one for an afternoon and intend to buy one shortly.

The Tamron 55-200 gets nice reviews and looks to be better than the sigma 55-200 and canon 55-200 usm ii. The canon 70-200 f4L is nice. (I should sell mine. edit: because I bought the 70-300 is. not because the lens is a problem.) The canon 70-300 IS is also nice. (That's the 70-300. Not the 75-300. BIG BIG BIG difference. Seems as good as my 70-200 through 200. After that it kind of falls off but isn't bad.)