If you're concerned with any level of quality, I'd stick with the mainstream distributors like digikey, mouser, and so on. I wouldn't buy a thing off of ebay. Too many shady sellers. With regard to stackpole in particular, as far as I know, while the company is US based, everything is all manufactured offshore. So like most components today, odds are everything is made in half a dozen production facilities. Line A goes to Vishay, line B goes to stackpole, etc. Same stuff, just different branding.