Sweet, I love grow ops open two ideas.... i have a few:
I'd say for a personal soil op with 2 dedicated flowering lights, go SoG + LST.
If you want to do away with AC, though your opting not to, I say use a Dual Cool tube 60" ($215:
http://www.thegardendepotinc.com/3764.html ) and you should be able to regulate temp way easier.
Also, you could get one 1000w hps and one 600w hps and let them start flowering on 600 then move on up to 1000w as harvesting supplies room.