Have you determined that the 135L will be too long now? Both are good lenses. I use the 100L on my 1.3x crop body but that choice was based on shotting a bunch of macro also.
I haven't used the Sigma but the Tokina 12-24 works good on the 1.3x crop body from about 14-24. Wider than that you get vignetting and hood interference. The 11-16 is nice but not much zoom on the 1.3x is usable from maybe 13-16 (might as well be a 15mm prime).
I didn't get a chance to try the 135L before I traded it, but that is going to be a while down the road. I now need to fill the gaps. I will probably get either the siggy or tokina 12-24 and either the 24-70L or the 24-105L and then I will worry about the 135 or equivalent. I just wasn't really happy with my first copy of the 24-70 even after I calibrated it, but I like the 2.8. Oh well, maybe by the time I am ready to re-buy the lens, the fabled mk II will be out

