Plum crazy is polymer and I personally would not get one. That being said, there are people on this forum who have one and they have not had any issues with them. Noveske and Spikes are good lowers, but I have not seen anything that would make them that much better than a $50 lower on sale from Palmetto State armory, all of which are made to "mil-spec" (not talking about billet LR). BTW, the MOE stock and LPK are still on sale for $125. If you plan on using Magpul MOE, then you might want to get this. I cannot find it cheaper anywhere else on the net.
I'm not going to rehash it, but this link will provide you some useful information about the different lower receivers on the market and why one may not be all that much better than another.
http://www.calguns.net/calgunforum/show ... hp?t=50947" onclick="window.open(this.href);return false;
You have not mentioned what the main purpose of your new build will be. Plinking, Home defense, hunting, etc, it does makes a difference on what parts you will want to build with. Personally, I would try to save money on the upper and lower receivers and then spend the savings on a better barrel from the likes of Krieger, Douglas, Shilen, etc, but mine is mainly for varmint hunting.