What's the reason for going quad over a more recent alternative? If it's for nostalgia, that's fine, but might grow into it's own thing and spawn another competition rifle. I say rifle because the idea of a turn-key upper, while noble, almost never works out. It's a willpower thing and who can resist the opportunity to build-up a lower to go with the hot new upper? I know I can't, nor can many people on this forum.