Because of the crowded road conditions, it seems to me unrealistic to talk about a "one-way" car and driver order on the Amalfi Coast. You can't expect them to pay for a two hour trip back home to Naples with their profits from your ride out.
It's not a comparable situation from Naples, but we ordered an 8-hour car and driver from Sorrento, using our big hotel's local travel services provider, and billed it to our hotel room. That was about 245 Euros, in 2014. The driver is happy to make visit suggestions, but you can be certain that he is a well-trained guide. He's a car driver.
Although you would have to check about when the Circumvesuviana stops running, you could possibly plan to have dinner in Sorrento after a car ride from there, and train home to Naples. Or get a quote from Naples, and see if it's worth it. BTW, you should download the Taxi Flat Rate PDF from the Naples government site. You'll want it in case some driver during the visit trys to charge you extra, and it will also give you a baseline idea of current (official) taxi fares. Naples offers flat rates almost everywhere between major points.
It might be worth finding out if a car ride from Naples can take a route that's NOT through Sorrento or Salerno, and thus, perhaps, less subject to traffic delays. It's true that you're almost off-season, but we're talking about a curvy two-lane road that doesn't permit two busses to pass each other without a time-consuming ballet.