I just went through the process of deciding what to buy for an 18" tube for a new build. Needless to say I couldn't settle, I'll end up with a Krieger or Noveske but in the meantime I went cheap buying an AR-Stoner barrel from Midway just to try out. I figured for $239, 223 Wylde, 1-8", 18" med-contour, fluted & black Teflon coated, it'll hold me over in the time that it'll take to order a Krieger or wait for a Noveske to be in-stock someplace. If it turns out to be a shooter I'll leave it on and just leave what ever I end up getting for a later date. How bad really can it be lol?
There's some great options (named above already) and some just depends on your budget. For me trying out the Midway barrel really isn't a big deal, no real loss if it doesn't pan out.