personally i've always stuck to kumho's. for the price they are awesome. never had a complaint on them. treadwear is good, when i buy the high performance tires they perform great. i've tried a few other brands and for the price, kumho's rock. if price isn't an issue, then yeah there are better tires, but you'll be paying double
for the 225/50/15's you've got a few choices and they're all around 100 a pop except the ast's. hankook ventus rs2, bfgoodrich gforce sports, some yoko avid t4's and the sumitomo htr200s.
for those stock 14's, you've got a few options. Bridgestone Potenza RE960AS Pole Position, General Altimax HP and those sumitomo's htr200's again are the only ones i'd recommend you looking into
what do you want, summer, all season, need a little more info here. and tirerack owns you, found 15 sets of tires for your wheels in 15 seconds.