definitely the right choice going integra, i used to get 600km out a tank and that was highway/city.
sunroofs leaking is quite uncommon.
if you go for a dc4, engines and gearboxs sell for nothing so even if you did have problems it would be cost $300 for a replacement engine.I do rate the b18b2 quite a well designed engine, always has enough power through the rev range.

the only problems i see with integras is radiator problems, mine leaked before 100k but thats a easy fix.