I have an 07 GT with stock 17" bulletts and stock Pirelli P Zero Neros. Now that I have a CAI and a Brenspeed 93 tune, I've noticed that its really easy to get sideways on a wet street. I'd like some tires that would be better in the rain. Also, I'd like a little wider tires. But I don't want to risk any rubbing or anything. Maybe a 255? I don't want to spend my life savings on these, either. And I'm happy with 17" rims. This is my daily driver. I drive on mixed freeways and surface streets.

What kind of tires would you recommend?

255/50/17 is the best fit, gets wider than stock, yet keeps the same overall diameter.
very popular among S197's with 17's that want a wider tire on the stock rim.

Anybody have any advice on which tires would be better for a daily driver that work well on wet or dry streets? I mean, which brand / model would be a significant improvement over the stock Pirellis but not cost an arm and a leg?

You could consider the fuzion ZRI's (http://www.tirerack.com/tires/tires.jsp?tireMake=Fuzion&tireModel=ZRi) or kumho SPT's (http://www.tirerack.com/tires/tires.jsp?tireMake=Kumho&tireModel=Ecsta+SPT) in size 255/50-17. They will both have better dry and wet traction than the nero's.

Michelin pilot sport a/s is a sick tire to go with if you want a good tire in the rain

Thanks, guys.