I've been busy buying stuff for my upcoming single turbo setup, and I'm well impressed with a couple of the companies I ordered stuff from in the US. The first one is called Vertex Industries / Verocious motorsport. They make pipe sections for making up intercooler, intake and exhaust pipes. I ordered a few polished aluminium pipes and silicon couplers on a Saturday night, they were here first thing on Tuesday morning, very cheap too and good quality!
Even better was ATP. They do Garrett turbos and associated connectors, flanges, bits of plumbing etc. I ordered a load of bits this Friday evening late, including my nice shiny new Garrett GT35R. They were the only place doing one with a 0.81 A/R GT4 flange with a Vband exhaust connection. It turned up first thing this morning (Monday) before I went to work. Very impressed.
Anyway, anyone considering piecing their own kit together rather than using one of the kits should definitely check them out. Ordered from both straight from the websites with no fuss & they take international credit cards.
http://stores.channeladvisor.com/verociousmotorsports
http://www.atpturbo.com/