If your commercial cows are producing quality calves, you could breed up to a purebred status, takes 3 crosses to reach 87.5%. Some breeds such as Charolais, Shorthorn though require a higher percentage to be considered purebred, 15/16.
Some of the herd books are closed, Angus and Hereford are. So if you are considering either of those breeds, upgrading is not possible.
It may be a little slower, but it will pay off in the long run. Commercial cows won't bring as much as it will cost to replace them with registered animals. By breeding up, when you sell the calves that are not kept for replacements, then you could use some of that money to buy a registered animal to put into the herd.
This will also give you some time to build a reputation for producing good cattle. This is very important for being able to market registered animals.
Do you know any of the breeding on your cows, Sires etc? What kind of records do you have on the herd you have now?