I'm just buying my first Impreza, but I had a Celica GT4 WRC before and after trying many tyres settled on using "Yokohama Parada Spec 2". They're cheap enough to trash through fairly quickly with, spirited driving..... Also handle very well in all conditions, and I think they look good too!
I've used many tyres from Goodyear Eagle F1 (old "v" shaped patterned ones" "Pirelli P Zero's" and other more expensive tyres that have been.