rakers8, welcome to the Seven Forums.
The chipset
drivers are usually not included in the beta or preview releases from AMD, but are usually included in the full Catalyst suite. Even if they're not they can always be downloaded from AMD as separate downloads.
As far as the video
driver goes, don't have a 5850 but do have a 6850, and haven't had any problems with the 12.1 Preview and if anything seem to be a little better than the 11.12 (smoother, image quality, etc). Getting them from XFX is of no benefit as they will have (if they don't just link back to AMD) the exact same
driver as what you get directly from AMD. There is next to zero difference between the
drivers from the card manufacturers and AMD, about the only thing the
driver from the card manufacturer might have different is their name shows up next to AMD's during the install.