Won't go cheap on a turbo; but IC core is fine... I'm using one from JustJap (600x300x100) and it works great; temperature differences are HUGE to say the least. At $300 for the core compared to $1000+ for a JDM similar, yeah why not.
Piping, bit of a hit n miss - I've seen really good stuff come from cheap kits, I've seen terrible stuff come from cheap kits. The JDM piping kits are precision made, fits first time every time. Easy fix - custom piping 1 afternoon, a mate, a bansaw, some masking tape and rulers and beer! Send it to your friend who welds alloy and its done. My FMIC setup cost me around $800 all up (core, piping, joiners, welding), still a whole lot less than going the JDM path.
Currently supporting 510hp without any dramas