Turbo boxes have no difference in strength apparently... but a slight difference in ratios? That's the rumour, nobody has really proved anything yet though and if somebody can, I'd like to know
And price wise, you're looking at definately under 1k with gearbox, loom, ecu etc.
Hell I sold mine for $200, although without gearbox Best to check NS.com and just search through the parts section to get a rough idea of what you're looking at.