I work primarily on 54mm, 75mm, and 90mm figures, so I hopefully can offer some good advice. You've already got some good company suggestions. For historical figures,
Pegaso is one of my favorite. You can also check out their sister company
Romeo Models. They've got a few fantasy figures too, but not that many.
Andrea has a lot of historical figures. In my opinion the sculpting on their older stuff is just okay, but their newer figures are very nice. Check out their Dark Nova series for 54mm sci-fi and their warlord saga series for 54mm fantasy.
For more sci-fi and fantasy focused companies, Scale75, Nocturna, and Ares Mythologic are great choices. Two other companies are M Proyec (
http://www.mproyec.com/) and Terrible Kids Stuff (
http://www.terriblekidsstuff.com/). They produce some really neat figures, although a lot are limited runs so their older stuff can be hard to come by. It's worth keeping an eye out for their new releases though.
There are also some neat figures coming on the market soon. One I'm particularly excited about is Black Sailors from BigChild Creatives. It's a line of orc pirate figures roughly 54mm to 75mm in size. You can take a look at their facebook page to see the figures:
https://www.facebook.com/Blacksailors/
They ran a kickstarter and are in the process of shipping to the backers. Once that is done, the figures should be available for regular sale.
Another cool line of large fantasy figures is Creature Caster. They also ran a kickstarter and are beginning production on the figures. These are probably still months away from regular sale, but it may be worth keeping an eye on.
http://www.creaturecaster.com/
And finally, since you're in California, I'd suggest checking out
RedLancers.com. They're a hobby shop in the US (over in PA) that carries a very large range of manufacturers. They've got decent prices and ship quickly within the US. It might be worth poking around their site too.
You aren't in Southern CA, are you? If you are, we've got a couple miniature groups down here that might be worth checking out. Oh, and since you mentioned an interest in samurai, you might want to stop by my
WIP thread. I'm working on a 90mm Pegaso samurai right now.