Hello John,
Another John from CA. Even with the idiotic laws here, there's still lots that you can build. I'm getting ready to start on my sixth AR. I have two 5.56's, a .308 and a pair of 6.8's. My latest guns, I've been building for accuracy, with the .308 and both 6.8's proving to be sub MOA capable. The great thing about the AR is that you can do anything you want.
If you're near any of the Crossroads of the West Gun Shows, it's not a bad place to check out all of the black stuff. Careful though, there's a lot of crap there mixed with a few reputable dealers. It's a good place for handguards, 80% receivers, accessories, some tools and an occassional great deal on drop in triggers. Generally, no descent optics, get that elsewhere. Optics Planet is pretty good. Try some different handguards, thought I liked quads, learned otherwise. I really like the Diamondhead VRS system. Easiest barreling job ever designed.
Don't scrimp on the barrel, AR Performance barrels are reasonable and accurate. You might consider the .223 Wylde. Melonite is great, as is stainless, with chrome lined being least desirable. All of my rifles are 16". That's just me, I guess, although my next build will probably be an 18" or 20" heavier gun. Another 6.8 SPC. I really like the SPC. I've taken two whitetails with it. Great hunting round.
Damned addictive building AR's can be. One more... Maybe... Two...
John