The R888s will blow the falkens out of the water.
Personally, for sticky rubber i would be going for re55s (or the new replacement of them from bridgestone forget the model), yoko a048 or maybe the fed 595rs-r.
The rt615s aren't a true semi slick but are a nicer all rounder tire for street. Good compromise but not good for just dedicated hardcore driving.
FWIW, my bestmate used to run a set of re55s, currently running a048s. Another mate runs r888s ad I used to run a set of rt615s on my mps3 and as for the 595rs-r...i'm just going off forum reviews and magazine reviews.
For a spare set of tires for happy days, i'd definitely get proper semi slicks.
GL and have fun!
