On street tires (true street tires, not drag radials or cheaters) 1.6 is about the best you'll typically get, as Josh said 1.7s are good, and 1.8s are average/getting bad. That is half a second faster just to the 60' mark from what you are running. I air street tires down to about 28PSI in the rear and 36-38 in the front - the pressure depends on the size and type of tire though, you want a good flat contact patch - if your tires break loose and you see 2 marks per tire on the outside edges than you need more air; 1 skinny mark in the middle you need less air. I have never launched at less than 1800 RPM and just go up from there until you can't hold traction.
LBZs have gone 12s on bone stock trans with a lift pump, and with a bone stock fuel system (no lift pump) and built trans - I don't know of any that have gotten 12s (or tried) on a stock trans without a lift pump, but I'm sure someone has done it.