My opinion on ebay turbo kits... seen a lot of them on the VWVortex, the manifolds can crack with extreme useage, and the sleeve bearings in the turbos are sometimes junk. Seems hit and miss on who gets a good kit, and who gets a pile of crap.
Consider these ebay kits "starter kits" like the crappy $20 tool kits you can buy at Walmart that "look" like the $200 Sears Tools, shit is gonna break and your gonna have to replace it. from the $1000 stand point, if you don't mind the idea that maybe a two years, maybe 3 months, down the road you might have to replace the turbo, the manifold, etc... go for it. These kits are essentially like doing Junkyard turbo setups, just more expensive and just as likely to fail, Just DO NOT skimp on engine management/fueling/cooling.
Personally... if you want to thrash on a Turbo (over boosting, etc).... ebay turbos are a FUCKLOAD less expensive to replace than a name brand one, sure you might spend $300/year replacing them, its "cheaper" than shelling out for one $1200 turbo