I have the same problem, but have researched solutions extensively online. I am 6 4, the car fitment isn't awful, but I do hit my head on the rollbar, which is a serious safety concern.
I'm not keen on the idea of the GT3 seats right now, but reserve my judgment if I get a chance to sit in them some day.
Looking at the stock seat, there is plenty of room to gain by going to a racing shell seat, and mounting it directly on the floor. That is the route I am going, having just ordered a Corbeau seat with a variety of rails and a tunnel seatbelt anchor to play around with.
You can also do a 'foamectomy' to make the stock seat thinner. Best done by an upholstery specialist. I don't want to modify the stock seat, though (keep it for resale some day).
Another option is the 'center console delete,' which is available from Porsche. It is merely a piece of molded carpet to cover wiring if the lower center dash console is removed. Trouble with this is that my 02 has the climate control module in the bottom of this lower dash, and it looks like it won't fit into the top of the dash where the cupholders are. Has anyone swapped an earlier climate control module into an 02?
pics here
http://forums.pelicanparts.com/showthread.php?t=447606