You can probably make the P5 handle better - I'd imagine the weight distribution is a little better with mnore weight over the rear. Personally I'd do the following:
1) Replace the swaybars with upgraded ones - that'll make the biggest difference, will stiffen the ride (even straight ahead) as it brings both shocks into play. This may be all you want.
2) Go to 17's with 205/45 or 215/45 tires (check the boards to be sure the set you purchase will fit). "1338" has a set of nice 17's for sale already...
The combination of 1 and 2 above gets you the majority of the ultimate grip of an MSP, without as much of the stiff-kneed ride that shorter, stiffer springs and stiffer shocks will bring. The 17's will give a sharper edge to the steering, and the bars will flatten the cornering.
3) At about 30kmiles, replace the stock struts and springs with newer, lower, stiffer ones. That way you have some time to evaluate the compromises this brings - and see if this will be worth it. The ride gets a bunch stiffer, ground clearance suffers, and your ultimate grip may not change - but you'll have more of a go-kart "feel". Replace them quicker if your wallet allows, but I choose 30kmiles so you get SOME wear out of the stock suspension - or replace sooner and sell the stock suspension to someone with 30-40k on their car.
4) IF your wallet can handle it, then upgrade the power using a bolt-on turbo kit (with boost gauge ALWAYS for an aftermarket kit), or do other power mods covered in other areas of the Forum. You want the handling and grip before the power if you can help it. Usually I'd also upgrade the brakes before adding power, but I've heard the P5's brakes are up to it. If you disagree, then do brakes before power (stopping is more important).
THEN you can head for the "car lingerie" department with spoilers, vinyl (worth 2/10ths in the 1/4 mile alone), etc.
Have fun - heck, it sounds like fun to me!
I dont ever regret it even though my P5 never gave me a whimper of trouble in the year I had it. 
