My opinion is that if you want a frame only? Santa Cruz, Trek, Specialized, Giant, Kona etc. all make good frames. I am a big pusher for the idea that it is preference more than brand on most of the "good" companies. I agree that the technology has changed quite a bit just in few years, let alone longer. Are you bike savy enough that you are going to build the bike yourself? You could always bounce ideas and components off of your local bike shop too. The guys at my shop will always talk about ideas and what I want to do.
Just remember also that if you buy off of Ebay, you will have no warranty. Don’t let anyone BS you otherwise. For example my Specialized has a lifetime warranty on the frame. Plus one year on all componets, I have had a few things replaced that I broke on the trail. All warranties I know of are void if you sell the bike to a new owner.
If you plan on getting back into it for good I would personally go with a higher end bike. Like a Stumpjumper etc. but that’s just my opinion.