Well you haven't gotten very detailed with the difference between the two setups. Is the higher HP one going to require larger cams with a rougher idle, or will you need a standalone? What sort of turbo(s) would get you the 500-550hp you're talking about? If it's just basic turbo upgrades, it'll be just as driveable as any other turbo car. Easy to drive around town, but wild when your right foot dictates. Another 100-150 hp isn't going to be a dramatic difference in driveability. You're still going to get the same gas mileage out of boost, just more power when you're at WOT and redlining it.

A larger turbo could even be considered MORE driveable, since you can rev higher without getting into boost, which is where gas mileage and traction start to decrease.