Sorry, I didn't realize that there were replies to this post- usually they get emailed to me and I hadn't received any emails. Anyway, thanks much for the replies. Some suggestions, such as buying a FF body and another lens, just aren't going to cut it, so I'm back to using what I have for bodies, and buying one new lens (until May...).
The t/s 17mm is, I think, the most obvious choice, however it is not slated to be released until May if Canon sticks to their timeline. That is fully two months away so a more immediate solution is at hand. In the end, I think I will go with the suggestion of the Sigma 12-24 and continue to use my existing 24-105 when possible. I do use an excellent tripod so will experiment with some stitching as well. This is temporary until the t/s 17 becomes available. I wouldn't mind having a super-wide anyway, and the price is right on the Sigma.
To Free1000, my typical client varies. All I really want to do is to be able to create a web gallery where what I do is shown off by the photography, not crappy snapshots that detract. I feel that with decent photography, my product is that much more appealing, and shows a higher level of attention to detail.
Pat