If you want to build one from scratch, that's great. I wish you nothing but the best, though I should warn you that it's rather addictive and can ruin your financial well-being.
Here's what I've found:
Stag lowers are great in quality. They are an off-shoot of CMT and you won't find better than that. The price for a stripped lower is right at $100.
Stag Lower Parts Kits are comprised of some of the best quality I have seen in any LPK's. I've looked at them all, and I can promise you that I will never use another brand - especially for a single-stage trigger. These things are incredible.
Building the upper is more problematic in that it requires you to buy tools that you can only use for building AR uppers. Factoring the price of the tools into the cost of the upper could mean that buying a pre-assembled upper is the better choice. If you don't foresee yourself building two or more ARs, shop around and find a smith that can put one together to your specifications. You get the looks and function that you want, but you also get their assurance of quality and function.
Personally, I will be building/buying a mid-length upper just as soon as I get employed again. It's addictive, for sure.