In my opinion, SOG is a good manufacturer. I would judge their quality as ranging from 5 to 8 on a scale of 1 to 10 (1 being junk and 10 being perfection). For any production/manufactured knife, this is a good rating. All of their knives are decent performers, but you've got to "find" the good ones hidden among the abundance of "decent" models.
I know for certain that some knives are made in Seki, Japan. My SOG Pentagon Elite II is one of them and is marked as such. Seki has a long history of knife and sword making and still puts out some of the finest traditional Japanese swords today. Though I'm pretty sure some of their models are also made in the USA, Seki isn't a bad place either.
As to steels, they have used steels ranging from BG-42 to the now more prevalent AUS-8, including VG-10, San-mai VG-10, ATS-34, 420, and OU-31 (sounds good, but I have no clue what it is).
All in all, I like their products, but I think some models are not realizing their full potential. Some examples would be using titanium liners (instead of 420-J2 or whatever weak liner material they use) in the PE II and other models which exhibit slight "give" in the handle, using s30v in the popular models like the Flash II, Twitch II, and Tridents, and giving the SEAL series some steel options - AUS-8 is a good choice (IMO), but it would be nice to see s30v or 154cm or, better yet, a San-mai model... options are always welcomed.
To the OP, if you go with SOG, you won't be disappointed - they make a good knife, but, if you want a truly "perfect" knife, SOG has a very few options. For a folder, look at the Vulcan series - especially the San-mai Vulcan. For a fixed-blade, I'm not sure you could find a reasonably priced one among their current line-up... it's a shame that many of their knives have beautiful designs and ill-matched steels.