You want a 1200 because they make about 100-115 RWHP and go from 0-60 in 3.0 sec. It does this on 87-octane! Then there are the easy upgrades to power offered by guys like Ivan, etc. But in its stock form, this bike is so brutal that mods are like ordering dessert with your dessert! Who needs to go over 140 MPH? And unless you hang a turbo on it, there is no easy way to increase acceleration anyway, apart from shedding weight (your own).
Then we have the insurance picture: Try to get minimum coverage for a Gixxer for $60 per YEAR (ha-ha).
The 600 is respectable, but makes more like 70 HP at the crank. What the RWHP is, I have no idea. But if the 600 does not meet your needs, find a used 1200 and sell the 600. Personally, I know why the Bandits are cheap, but I fail to see why there have not been bone - crushing stampedes to buy these bikes at the asking prices. Fear, maybe? Many cruiser riders can not handle the power. All I want now is a 1400 Bandit!
Herb
There is no substitute for cubic inches.