Given the high build quality of the Model 6/2 amps and fact that most were manufactured only ten years ago or so, it is quite unlikely that the caps on your amps need replacing - depending upon how many hours an amp has seen, caps can easily last 15 to 20 years, and often much longer.
Take the top off of your amps (after disconnecting the power cords and the battery power supplies, if you have batteries) and look at the caps - if any of them seem to be misshapen or look like they are leaking, then replace them. This can be done by any experienced tech and should not cost more than $500, and probably much less - unless there is something unusual about their design that I'm not aware of, there should be no need to ship them off to Rowland for something as simple as replacing caps.