As far as I know the only model you can now purchase off the shelf with a threaded barrel is the Tac…
I could be wrong but from what I've read and understand this is the case.

Cheapest why to get what you want…purchase a varmint model and have a smith do the work.

If you are just looking for a shooter…the Tac model is over priced IMO and the barrel does not shoot any better than a regular varmint model.  The regular varmint has actually proved to be the winner for all range shooting we do.