Judging from the availability of kits and such right now, I'd say if you are looking to pick something up before the end of the year....your best bet might be to pick up a complete upper and a complete lower and put them together. As someone already pointed out, you will save a few $$'s doing it that way, and it will give you somewhat of a feel of 'assembly', even if you are only pushing two pins. I think you would be hard pressed to find all the parts necessary to build a complete gun from parts right now, and from the sounds of it, it may be 12-16 weeks or more before stock gets replenished.
On the other hand, there are still a few complete uppers and complete lowers out there, without the long waits. I just picked up a complete RRA (Rock River) upper last week, only 4 days from order to door. That being said, the choices are more limited than they were last month at this time, but you should still be able to find something that will fit the bill.
Locally, lower assemblies go very quickly, like some folks buying 5-10 at a time
Ahhh, but the beauty of capitalism, those same folks are posting on the Equipment Exchanges, Craig's List, etc, trying to make bucks off of all this.
But do some searching on here, you should be able to find a few threads with links to sites that members have used and recommend. Brand wise, what you mentioned works well. It all depends on what roll mark you want on the side of your receiver, just as it is up to you what brand of jeans/shoes you wear, or what car you drive. Is one better than the other, in the lowers, as long as you are staying with the main brands, away from anything CAST, then you are pretty much good to go.
Sure there will be some that scream Mil-Spec is the only way, or you have to use this brand over that one, or whatever. At this point in the AR game, I don't think there many out there, at least not in the main brands, who are trying to cut corners by slipping out some junk, or anything that would not hold up to designed use.
Same thing with the uppers. There you can find some differences in barrels used (manufacture, material-stainless,chrome alloy, twist ratio, etc), or the bolt carrier groups, flat top w/ or w/o handle, A2 with built in handle, etc. If you are thinking scoped, I would recommend the A3/A4 flat top uppers, and not pay for the removable handle - no need for it. That will also save you close to, if not over, $100.
Actually, I like what you had in mind, with the 20" Wylde chamber, but then again, that's just my personal preference. For a first time gun, I think that would offer you the best overall performance, with just about any ammo out there. Also, try to find that same barrel with a 1:8 twist ratio, and you'll be good for ammo up to 75, maybe 77 grain. Again, just my personal opinions there.
With the upper, lower, you'll be close to that $1000 mark, so a scope would be additional $$'s. Here, the sky is the limit, as I have scopes on my AR's that range from $30 no-name red dots, to Schmidt & Bender tactical scopes. It's all in what size wallet you brought, what your needs are (as defined by yourself), and what feels comfortable to you. Sure, we can all (collectively or individually) tell you what to buy, based on what we have done personally, or in some cases, what whoever said, or read somewhere else. But bottom line is, it's your $$, and your happiness or regret, at the cash register and when you get it home.
So do your homework, ask away with any questions you have - we'll try to help as much as possible, let your fingers do the mouse pushing and research online for brands and brand reviews (lots of gun magazines, tactical sites, etc do reviews on most of the major brands and models and post their reviews on the net), if you have time, go to a local range that may have a few models to rent, or ask to shoot friends guns and ask them what works and doesn't work for them...and why. That should give you enough info to help you make the right choice. But don't hesitate too long, or you may be waiting for a WHILE