Ok, so I have thought about buying an Armalite upper and lower to put together. Costs more than the RRA I was thinking of doing, but there are also some differences I was curious about.

The armalite A4 carbine comes with a gas block front sight base, instead of the A2? style one on the RRA. I want a front sight, as I was plannign on starting with iron sights. What are my options with the Armalite? I see that they sell a detachable front sight for $50, but it doesn't look the same.
The carbine and other Armalites comes with an optional 'recoil check'. I had not planned on putting anything on the end of my barrel. Does this 'recoil check' do anything useful, or is it more for looks? Is it one of those that makes it louder when firing or anything?

Just a few questions at the moment. I don't know that I will go Armalite, since it is more expensive, but isn't it better and not just a higher price? I like the chrome lined barrel part, plus I can buy it somewhat locally and save on shipping, FFL fee and time in getting it. I just don't want to get it just because I am in a hurry if maybe I shouldn't.
Anyway, thanks for any help with this issue.

Deniro, I wanted an Armalite, but ended up getting an Eagle lower with the match trigger, and an Armalite 20" A4 upper.  The match trigger is very nice compared to my other non match ARs, and I've been very happy with this setup.  This rifle does .5 moa pretty much all day with my handloads, and I don't think I've ever had an FTF or FTE in this rifle.  I've shot Wolf ammo, SA surplus, and handloads with nary a hiccup.  

I have the detachable front sight and handle, they work fine.  I got mine from Armalite, but there are others out there that are just as good and a few $$ cheaper.  

The recoil check on my 20" makes the rifle shoot very well, and doesn't seem to be very loud compared to my non braked M4.  I think the shorter barrels are a little squirrely anyway; I just had my M4 at the indoor NRA range last weekend, and forgot to bring ammo...so I bought some cheap ass federal .223 ball they had...the report was punishingly loud...everyone stopped and turned around...and there was 2' of flame coming out ot the muzzle.  I don't know what the hell kind of powder Federal uses in those rounds, but they are nasty.  

I've got 2 16" RRAs, and both of them have noticeably more recoil than the 20" Armalite, even the varmint barreled one.  

I paid $350 for the lower with the NM trigger, and $450 for the upper.  Quantico arms has Eagle lowers with the NM trigger for $325, but the uppers have gone up, I think they're all $500...use these prices for reference.  

Armalite makes a fine rifle, in my limited experience.  I don't know why some people hate 'em so bad, but I love mine.  

edit: I think the reason my upper was only $450 is I didn't want the carry handle/front sight combo...I think they knocked $50 for that.  

You won't be able to purchase an ArmaLite lower... ArmaLite lowers are available only as complete rifles.  ArmaLite may cost a few dollars more, but the quality of build along with a lifetime warranty are a big plus in favor of going the ArmaLite route instead of an ArmaLite upper with a 'whatever' lower...