Any of those manufactures is pretty reputable. I would have no issues buying from any of them. However, I will make comments on the specific models you listed.
MSI HAWK: Best cooling and potentially better overclocks, cost less than the Vapor-x
Sapphire VaporX: These models are ALWAYS overpriced from Sapphire. Still Sapphire is a good brand.
XFX: doesn't have an aftermarket cooler for the 5770, they use the 2 reference coolers and that is it. However, they offer the best warranty.
Price will depend on where you are and where you can buy it from. If you are in the US- go to Newegg.com and look up the 5770- see what you find. I would honestly go for the cheapest you can find for any of the brands you listed as they are all good.