Well, I ordered my first parts tonight for this build.
I decided I'm going with a rifle length set-up. Most likely a 20" barrel. So for now, I'm gathering parts to build the lower. I ordered a Magpul MOE fixed rifle stock with buffer kit. Got it from Buckeye Tactical for $99 plus free shipping.
Next up is the LPK. I want a half decent trigger, but I'm not ready to shell out for a two stage. I'm intrigued by the BCM enhanced lpk, but it's out of stock pretty much everywhere.
For now the plan is to finish the lower as soon as I can, and use an existing upper. I'll be piecing the new upper together over the next year or so as funds allow.
I'm going the other route. I'm building the upper first. I'm going with a 20" as I only have 1 of them and it's a Rock River Bull in stainless. Sucker weighs a ton but is very accurate. I'm wanting a 20" I can shoot free standing or on a bipod. Plus being able to suppress it is a plus. I plan to finish it with parts from the 1500 then start getting the parts for the lower. Hopefully Allen will have some deals on optics!