I'd look at the 55-250 STM. From what i've read, it's a hidden gem in the EF-S lineup. Here's the TDP comparison b/w it and the 18-135: http://www.the-digital-picture.com ...omp=0&FLIComp=5&APIComp=1
The 70-300L though.. much more expensive, but by all accounts an excellent lens. If you can swing the cost, that's what I'd go with.
I've heard good things about this lens. I could never bring myself to spend $1,500 on an f/4 zoom, especially since the 70-200mm f/2.8 is about the same price. Also, the new MII non L version is under $500 and has great reviews. That's just me.