Not to hijack your thread but I saw a Troy upper for $699 at a local gunshow, I asked the old folks running the booth if the made a mistake. They told me the price was correct, they also said it was ordered from Troy and was all original. If I had the money it would have been mine... Oh well, it wasn't meant to be :-(
No experience with a complete Double Star gun, but I used a Double Star barrel and BCG in one I assembled for myself. I used the 16" fluted stainless bull barrel and BCG that Brownell's sells. The price was decent and everything went together well, with a tight fit and no issues.
I've only had that carbine to the range once so far. The first group was larger than an inch, but after that the gun and I settled down and it printed three honest, five shot groups of a hair under an inch using handloads. No malfunctions. The barrel cleaned very easily. Very promising performance so far.