Clack is probably the best valve there is, especially for a DIYer because there are very few parts and it was designed to be the easiest to program and repair.
Entry level... the quality doesn't vary from one version to another.
Dealers are not supposed to be able to sell just a Clack valve, and I doubt you'll find any selling it online but, you say "system", I take that to mean a complete softener. If so you need to know how to correctly size a softener to know if this one fits your peak demand flow rate and salt efficiency capacity needs. You can click on the link in my signature to learn about that but what size is the one you're looking at and what is your water quality?