Hey Zilvia,
Sorry for the lack of official introduction, but we felt we had to chime in here...
-Ball Bearing turbos can be rebuilt (we have an upgraded ceramic ball bearing rebuild kit, Garrett is steel ball bearing)
-Genuine Garrett ball bearing cast compressor wheels can be bought separately
-Genuine Garrett ball bearing Billet GTX compressor wheels cannot be bought separately (at this time)
-PureTurbos does have over 600 different billet wheels available including 11-blade extended tip wheels (PTX Wheels) to fit Garrett ball bearing turbos and most other turbos (GT28, GT30, GT35, 18G, 20G, 60-1, 18T, 50trim, 57trim, 60trim, etc...)
-A properly rebuilt turbo (journal bearing or ball bearing) needs to be component balanced AND cartridge balanced to meet industry standards for balance tolerances
-Cartridges which are only component balanced are usually 1.5-2.5 gr/in out of balance when tested on our cartridge balancing machine. After being balanced on our machine, they come out between 0.01-0.08 gr/in
-PureTurbos does have a cartridge balancing machine (all our turbos and rebuilds are cartridge balanced). Most turbo shops do not have a cartridge balancing machine
-Precision Turbo does NOT have a cartridge balancing machine, only their "aftermarket replacement" line are cartridge balanced (because they are assembled elsewhere, not in the USA)
-Turbonetics does use a cartridge balancing machine
These are just facts, feel free to ask questions and we will do our best to answer them.
PureTurbos
Oceanside, CA