I have the 7.5" Model1Sales pistol kit on a Spike's stripped lower. I love it! No problems with it at all.
You might want to consider pricing out the parts you want and assembling 100% of it yourself. You might save money. Then again you might not "save money", but you could end up paying the same, get exactly what you want and not have to pay more in the future by replacing parts.
It doesn't take much at all to assemble one yourself. A vice, cheapo upper vice block and a torque wrench is about all you need in the way of special tools. Watch the Brownells How To Build An AR-15 Video and you'll see that there's not much to it at all. Start shopping for a barrel, stripped upper, stripped lower, hand guard, BCG and lower parts. Many vendors will check headspace before they ship it out if you buy both the barrel and BCG from them. Some vendors will check headspace for you even if you ship them the BCG.