RRA is a tier-2 manufacturer. Only Colt is Tier-1, LMT comes close, some variations of custom builders (CMMG and Noveske) do, too.
This chart has become ubiquitous, but take it with a grain of salt:
That being said - Del-Ton & other bottom-feeders are as low as you can go.
You don't need to spend a ton of money on an AR upper & parts, but the quality difference at $500 and $800 is much more than double.
A couple of things to note about that DTI kit - trigger, no chrome lining in the barrel, and built with random parts by random manufacturers. That Stag uses some of the same barrel doesn't mean that somehow that barrel is good. It just means Stag isn't very choosy, either.
My advice is this - don't bother with a kit. It forces you in a box for parts selection and gives the illusion of easier. It's not.
Here is ALL you need to build a Cali-Legal AR (along with my advice for stuff):
Immediately DROS the lower... now... today... the rest will come along during your 10day wait.
2.) Lower parts kit
3.) Complete upper
5.) Buttstock kit (stock, tube, spring, buffer)
6.) Compliance parts (bullet button or MMG)
8.) LOTS of ammo.
Here are my suggestions - I'd push you toward a Recce build:
1.) Build a 16" (or maybe slightly longer), with a medium or lightweight barrel contour. It will let you get good accuracy and be able to carry it.
2.) Get a mid-length gas system (unless you meet/exceed 18")
3.) Get a 2-stage Rock River Arms trigger with your LPK. It's well worth the extra $80. My personal favorite LPK is Armalite, but save money by getting the combo NM RRA kit (RRA is my 2nd choice for LPK). If you're trying to save money, just buy the standard LPK. The upgraded trigger is my 1st choice in "upgrades."
4.) If you want, get a Daniel Defense, Troy, SWS, or LaRue railed handguard - if you can afford it - and put it over a mid-length low profile gas block - looks cleaner and will allow you to mount a flip front sight on the rail with a longer sight radius. If you can't afford a free float rail, get a standard fixed FSB with a plastic handguard. It's cheaper and functions well. Having a flip front sight is unnecessary for almost all builds, but if you really want it I'd suggest one built into the gas-block.
5.) The meat:
Get a flat-top upper. I'd go with the following upper/barrel manuf's (best down - all are very good): Colt, LMT/Noveske (tie), CMMG, RRA. The CMMG is probably the best entry-level value with the most options, but Colt and LMT build better products. ONLY Colt and FNH are actually mil-spec Tier-1 manufacturers. If money is no object both LaRue and VLTOR make some very, very nice uppers. Skies the limit on barrels, from standard USGI stuff, to White Oak Armament, to Douglas or Krieger... Pick the best quality upper and barrel you can afford. Make sure that either the barrel is chrome lined or it's made from stainless steel. Get M4 feed ramps, extended. If possible, get an enhanced bolt, this makes a big difference in reliability. You can leave it off and add it later, if needed. An enhanced or M16 carrier is a good choice, too.
6.) Pick your brake or flash hider. This is a pretty personal choice. The best FH: Smith Vortex. The FSC556 is pretty hot right now. Brakes have many options. Keep in mind neither really do much - the .223 is limited in recoil and how often do you shoot at night? For cost savings a standard, cheap A2 is just fine. I recommend having a muzzle device of some sort as it keeps the muzzle from getting damaged.
7.) All collapsible stocks are chasing the stability of an A2, which is the best choice economically. Most people prefer the collapsible. If you have money to spend, get an LMT SOPMOD buttstock kit. Magpul UBR, VLTOR EMOD and Magpul CTR are the next choices, in that order (except the UBR is probably MUCH too heavy for most applications and still isn't released). Price pretty much follows the quality there. The best cost/quality point is with the CTR. If you can't handle the price on that, the RRA collapsible will do. If possible, get a Mil-Spec carbine buffer tube. It will allow easier future upgrades.
8.) If you have money, pick an aftermarket grip. The MIAD is the hot one now. TangoDown, Ergo, Hogue etc all make their own, too. You don't need to change from the standard in the LPK, but it's nice.
9.) The best flip sights, hands down, are Troy. If cost is an issue a seller here on the boards has USGI Matechs for $55 (about 40% the Troy).
10.) Get one 10/30rd mag for pics (Magpul PMAG looks nice and functions well) and a few more 10rd C-Products + Magpul ranger plates for shooting
Other needs: Case (soft is best), sling (I prefer 2-point, 3-pt is acceptable, 1 point is stupid), optics (EOTech for 0-150yds and SPEED, ACOG for 50-400yds), ammo (anything cheap and brass cased, preferable, but Wolf runs fine - if your range allows magnetic ammo). Lastly, the Magpul winter trigger guard really finishes the look of a rifle.
Use this thread for guidance
Keep in mind that some information in that thread is out of date (be sure to look at posting date). Almost all "new information" is toward being more liberal, than conservative.
This is also a nice summary:
For vendors, use those that support us as a community:
I've personally had good dealings with: