I don't think your limitation is your action. Your limitations are that you are shooting factory ammo through factory barrels. Before you go dumping a lot of money into a custom rifle
, you really should start handloading.
My advice is to get a good single stage press, a good beam scale, a basic lathe style case trimmer, three or four reloading manuals, and dies for both rifles. Be selective about your reloading components and buy them in quantities you can afford when they are available.
Glass bed your rifles in their respective stocks, making sure to free float the barrels, and put decent glass on them with plenty of internal adjustment. Once you have developed good loads for your rifles, shoot them until you have worn out the factory barrels.
When it's time to hang new barrels on them, then decide if you want to go with a different chambering. By that time, you should have the skill to exploit the accuracy of a custom barrel and increased ballistic potential from going with something more powerful.
You can focus on pouring money into a custom rifle
if you want to, and there is nothing wrong with that if that is truly what you want, or you can focus on improving the nut behind the trigger. I believe that putting your time and money into honing your skills as a rifleman and handloader will pay bigger dividends in the long run.