SO this comes down to how much you want to spend initially. Pete at AR15SALES.COM is going to beat most other folks on RRA, LMT and STAG both for parts builds and full weapons unless you stumble on to a great deal with free shipping (which Pete does on most things anyway).
Accessories are going to cost what they cost.. and you do get what you pay for no matter what anyone says here, as for a significant savings with the add on parts and building from the ground up, that would mean skipping the completed upper etc.. I'm not going to agree that you will save a significant amount of money on that. Complete rifles are at about the lowest price we're going to see for a while. You're noting that you don't have a ton of spare time, so I'm going to say that your choice should be based on a few things..
1. Do you want to put it together yourself?
Some folks like the idea of getting to know their AR better by doing it this way. If you're not overly interested in the super fine details, then this might not be for you. It isn't anything resembling difficult and there are plenty of instructions that will get you through the lower assembly. The upper assembly is another matter.
2. What's your initial price point?
You noted that this wasn't really an issue, but I say that it is. If it isn't an issue, then talk with Pete or someone like him that has a fine reputation and just have them assemble the weapon configured the way you want and be done with it. You can always reverse engineer some of the stuff like the lower and it's parts if you're really set on learning that, or just read the build guide at ARFCOM.
3. Are you going to be a Brand Fanboy?
If so, then just drink the cool-aid now and buy a Colt so you can sit around the keyboard and espouse the greatness of the Colt Cult
Personally I don't subscribe the the much vaunted/hated chart supplied above. I know it comes from a big name and someone who has shot more AR's than I've ever owned, seen or dreamed of (OK well I've got a vivid imagination, so maybe not that last part) ... so take my advise for what it is.. coming from someone who doesn't know or owe you (for) jack diddly. Get the weapon you want, built or build it the way you want. I personally have had great experiences with both RRA and STAG, I do own a Bushmaster that has been.. OK considering the age and abuse it (and all my weapons) gets. I won't buy another one though.
Again, take all of that for what value you find in it. I honestly just don't care what you buy or configure as long as you get one. The more the merrier and the Disease will feed itself
