I have used two Doublestar kits in Sabre lowers. The trigger isn't great, but not crap either, but all of the parts fit very well. I have seen several people recommend Stag, but haven't gotten to try them yet. I will for my next build. Haven't heard anything on the kit in question.
What will be the main purpose for the rifle? If it is just a plinker, there are several. If you want stainless parts, there are some out there. Most people worry about the trigger. My build is a KISS theme, and the trigger is perfectly serviceable. I couldn't resist tinkering, so I polished the contact surfaces. That slicked the pull up a bit. Just watch those detents!