Bushmaster carbine = $850, 20" HBAR = $868. A3 with removable carry handle. Houston gunshow.
Doublestar seems like a good value, a friend of mine has a carbine & is very happy with it, says it's very accurate. I've not heard any bad reviews here on THR.
Definitely get the A3 flattop.
DPMS comes with a chrome-moly barrel, not a chrome-lined barrel. I don't want to get into the pros & cons of that, just be aware.