Not only does Sannie and friends tell you which arent stable, but they can give you a pretty good break-down and description of what phenos to expect and which to look for, with grow information on each and all of them. They arent just f1's tossed together and sent out the door. They grow out alot of their f1s to see if they are going to retain what they are going after.Just to be clear, there is a significant difference between good breeders and houses that sell good ceeds (but don't necessarily breed or stabilize them). Unstable lines can still make great plants, they just may not all look the same, and they may not be suitable for further breeding.
Reputable top "old school" breeders include: Shantibaba (of Mr. Nice ceeds), DJ Short (creator of the famous Blueberry strain), and Sam the Skunkman (for his work on the original Skunk #1, and others). All of these put out (or have put out) inbred stable lines.
Serious seeds has multiple excellent inbred stable lines, including AK47, Bubblegum, etc.
Sannie and the breeders he works with have a lot of good lines in their lineup, though many aren't really stabilized. In fairness to him, he does indicate which are and which aren't, and his reputation as a businessman is absolutely stellar.
As as above, there are any number of other houses that offer great ceeds, but that doesn't necessarily mean they are great breeders or the lines are stable.