Depending on how much you want to spend - Transition TransAM would be worth a look. Horizontal dropouts so SS compatible, has a deraileur hanger for geared as well. Only dislike is the top tube cable routing - they have 2 frame cable holders, but you have 3 cables if you're not running SS.
I just bought a frame off here and built up with a 140mm 454 Pike and it goes alright. You'll soon get into the alum / steel argument with hardtails, I've come from a Norco Manik to the TransAM and can vastly notice the difference on rear end compliance, although the manik is constructed to be a rigid as a light pole, the Cham might have some flex in the chainstays?
I was looking at the same thing - wanted a longer travel HT all day XC/AM bike (also have an GT i-drive 4) and was originally looking at the Chameleon, then after a bit of research got looking at steel.
My 'research list' is pretty much what was already covered here:
Santa Cruz Chameleon
Transition TransAM
On One 456
If you want alum, the SC Cham will be hard to go past.