It depends a lot on your rim width, and again you're also hemmed-in a little by having to be within 3% of your overall OEM diameter.

For instance, on the tires...

The OEM specs for 19" PS2s is:
front - 235/35-19 - overall diameter=25.5"
rear - 265/35-19 - overall diameter=26.3"

If you have 18s, the diameters are 25.3"/26.3" respectively.

For the 20" you have:
front - 245/30-20 - overall diameter=25.8" - a good match
rear - 285/30-20 - overall diameter=26.9" - a good match
rear (alternate) 295/25-20 - overall diameter=25.8" - a good match - except that 295 would probably be just a little too wide to use on the 10" wide rim you have - 295 would be better used on a 10.5" or 11" rim. 285 is best used on a 9.5" to 10.5" rim. A 295 tire on a 10" rim might give you a little too much sidewall flex, imo.

I don't see a 275/30-20 PS2 on Tirerack - only a 275/40, which is waaaay too tall.

You should do this math on any tire you'll likely use on the new rims... I'm assuming you have the offsets figured out. Staying within the 3% tolerance for the overall diameter is very important if you want your electronics to work properly... and I would recommend staying with the brands and models of tires that are Porsche N-spec for the car. If you're not sure what N-spec is, do a search and you'll find it - there's been plenty of earlier threads on the topic.

brad