So i have plans in mind to build my first SBR soon. I believe i have a hookup to get a spikes tactical lower but not sure which lower parts kit to get. I would like to keep it at a decent budget but not skimp. So my main question is... What upper should i get? I want something with an low profile adjustable gas block, approx 8-10" barrel threaded for a future can. I understand all the rules of class three, so i'm just trying to figure out which parts i need now so i can get it rolling... IDEAS? Then i can try and figure out which CAN i want.