TOTW is okay, good to deal with to a point. The Issac Haines/ Bivins kit is alright, no unseen problems that I've ever had. Thier French Fusil kits are a different story, stock problems on two that I built. Jim Chambers kits are top notch. For a little more money, the Chamber's kit is what I would go for. Little bit of a hassle sometimes to get barrel delivered at the same time as the stock, but worth it. Get Chambers white lightn' touch hole liner w/tap and drill bit, very fast ignition. TVM's are supposed to be okay, never used one of thiers. Dunlop puts out a good kit, he supplies stocks for a lot of the dealers, very good quality grain-wise. Built straight barreled kits from Pecatonica, but haven't used any with taper/flared barrels.
Double set triggers are okay, especially for target work, but I perfer single triggers. Doubles can be hard to get in correct position to use for both set and unset. Single triggers can be positioned for great pull wgt. There's lots of good books out there for reference on building, if you don't have any, get at least one to help ya.