There are plenty of rim options available for your car. For starters, check out tirerack.com. Enter your year, make, and model and start your search for wheels! Plenty of results to be had there. I'm not sure that you can use your Porsche center caps (with the logo) but you might be able to for some.
Here's a good source for replicas -It's where I got my rims:
http://www.wheeldynamics.com/
Another good source, authentic and expensive:
http://www.wheelenhancement.com/
And lastly, eBay
http://www.ebay.com/
eBay is also a good solution for what you can do with your old rims when you get your new ones. It's nice to have those offset the cost of your new ones. They'll fetch some decent cash, as they will make a good track set for somebody. I had the exact same rims as you and sold them on eBay... they found a home on a Porsche 968. (actual photo of my rim's new home)
If you don't want to deal with eBay or shipping rims, try CraigsList.com. It's can be more local -and it's free.