They may be a bit intimidating to consider building, but buy Zediker's book on building a competitive AR and he walks you thru it. They're actually fairly simple if you have much in the way of technical skills. Might be a good first purchase regardless of what you end up doing.
Amazon product ASIN B004NB1BSC
Quite a few, though not all of the premium barrel makers offer a complete AR barrel. The best shooting barrel that I have is a Rainier Arms "UltraMatch". It is not the most expensive AR barrel that I own, but it is on the upper end. If going with a .223 I'd go with the "Wylde" chamber variant.
You'll likely need a bolt for the barrel maker to head-space to. Some barrel mfg's offer their own bolts, but some will H-S to your bolt. I've bought many complete BCG's and bolts, and I keep coming back to Lantac's offering, so those are what I send out.
For an M4 or carbine type build I use ALG's ACT trigger assemblies exclusively. For a PRS type of build I'm all over the map and don't have a specific favorite although the Jard and the Calvin Elite are near the top of that list.
Sprinco for the recoil springs unless using a JP Ent. "Silent Spring" assembly.
Superlative for adjustable gas blocks. Most of my builds have not needed an adjustable gas block (just buy the Sprinco spring by the application and it works well), but two of them did and I am thoroughly impressed with how easy it was to tune them and get the rifle functioning smoothly and reliably.
Ultra short and/or light M4/carbine builds get an B.A.D. Sabertube butt-stock. More 'normal' length M4/carbine builds get a Double Star ARFX butt-stock. Rifles get a Magpul PRS.
I really prefer Apex "Gator Grip" forearms to anything else that I've handled.
A.R.M.S. for iron sights. For plinker I've come to really like everything about the Bushnell AR 1-4x's in a Burris PEPR mount except for the scope's weight. I think that they punch well above their price point.
Can't go wrong with either Blue Force Gear or Magpul for a sling. I like them equally well.
If a partial assembly works best then I'd give good thought to the White Oak Armament link on the first page or a Compass Lake upper. Buy one of their complete uppers and match it to whatever you decide to do for the lower.
Best choice of rifles, barrels, accessories and custom work!
compasslake.com