What kind of games do you run mostly?  Eight gigs is fine right now for just about everything.  Only a handful of applications, like a heavily modded Skyrim for example, are starting to use more.  Since I just started playing Skyrim myself I might personally go with 16GB (which would require you to upgrade to a 64bit OS as well).  The only concern I would have is that DDR4 is supposed to hit the consumer market towards the end of this year...maybe.  Well, it's a tough call really.  The release time-frame isn't set in stone and it will almost certainly be overpriced at the beginning AND it's going to require, at the very least, a new motherboard.
Anyway...as for brand-names, I trust Corsair, Mushkin and Samsung.  G.Skill is another popular brand among gamers but I have not personally used them before.