[ezmaass]

Personally, I wouldn't do it.

Here's the upgrade you need --> M6 GC.

The 650 GC is a nice sporty grand touring car, but when you start talking about modifications like LSD, downpipes, etc, it seems counter-intuitive to me. It's a really big (physically huge) and heavy (4300lbs?) car. It's several feet too long and about 800 pounds too heavy to be a great handling car.... and while the power is decent (445hp), the weight isn't. The M6 compensates with much more power, a much better suspension, and importantly... better brakes! The brakes on the 650GC are considerably underwhelming for a car that could be driven in a sporty fashion.

In short, I'd avoid throwing a lot of money into trying to make the 650 anything but what it is... a sporty grand touring car with a lot of luxury. Don't get me wrong - I love it. But I'd say it's akin to a Gulfstream jet... very high luxury environment to get you from point A to B fast. But it's not an F-22, and while sporty, it won't maneuver like a fighter jet.

If you want a GC in a much sportier package, I'd just upgrade to an M6 GC. If you want an all-around much sportier, better handling car, I'd move to a different class of car altogether.