The problem of changing from a Mk2 FRS is that most cars are a backwards step in power/dynamics unless you throw muchos cash at them on modifications. Of all the things id expect you wouldnt be happy about sacrificing, id bet its grip most of all. So that narrows the market right down IMO. You have either AWD cars ie S3 or R32, or you have the FWD hot hatches with LSD as standard.
That leaves some tidy motors though
Megane R26 230F1
Mk1 Focus RS
Civic Type R Championship Edition
maybe throw in a wild card
Mazda 3 MPS
Those Mk2 MPS's will give a FRS a run for the money and come very highly spec'ed with gadgets inside. Plus you get a plate differential.
Or you could get a mk1 S3
Id choose all the above cars before a Mk4 R32 tbh. The R32 brings a lovely engine note and good grip to the party and thats about it IMO.