Realistically, if I want to be completely honest, no, you don't need more than that.
When I was at 560, the car was already very quick. Now, however, it's more of a monster that no longer runs out of steam at around 110 mph and demands respect 100% of the time. So does one need 730-740 or more? No, but it's fun
One more thing, my power level is probably the top end of (or a bit beyond) what you can put down in a RWD car with "normal" tires. What I mean by that is tires that can be used in any weather you'd want to drive a Camaro, temps ranging from 35-40 to 100-105 degrees, dry or wet or downpour, which I'm sure you also get a fair share of in South Florida.
I run Michelin PS4S, others swear on the Conti ExtremeContact Sport 02, both excellent choices that can do all of that. My meaty 315/30 rears can hook from a 20-25 roll and then the car pulls like there's no tomorrow. Not from a dig, but that ship has probably sailed for you as well.
Any more than this much power, and you're in drag radial territory with serious compromises.