I have the Michelin Pilot Sport's on the GT5 and they are a good all round tire, performed well on track in the wet (full monsoon those 2 days) and dry.
The second Pantera is shod with Toyo R888's but that's an 18" wheel
I also have Pirelli Assimetrico's on the Ultima and apart from the sticker shock they are an awesome tire, that said I do run Hooiser R6's in the dry.
For Infineon this time of year you are probably wise to stick with a treaded compound.
I know a few people that have stepped down to a 315 width and prefer it especially for track. There's a whole lot more choice and availability at that width. The Kumho's or R888's come highly recommended.
http://www.tirerack.com/tires/...diameter=17&x=10&y=3Julian