The 24-105 is a better deal if you don't need the extra stop and supposedly has more consistent quality control than the 24-70.
Do you really need a zoom? Two primes would be sufficient when paired with your other lenses. 22mm vs 24mm on crop is negligible (and no one makes a good mid-range 24mm) so I'd just jump into a 28mm\30mm and a 50mm\60mm would cover all the bases. $400 primes are sharper and produce better images than L zooms.
EF 28mm F/1.8 USM,
EF 50mm F/1.8 USM,
EF-S 60mm F/2.8.
I also really like the
EF 85mm F/1.8 USM, 85mm is my favorite focal length on crop for portraits/nature.
Because you have micro-adjust in the 7D you should also consider the Sigma 30mm f/1.4 and Sigma 50mm f/1.4 which have shown to be sharper than the Canon equivalents but need MA to get the full effects of it.