I've read in previous threads about noise problems that some people have used DC-DC converters to get rid of the noise without degrading audio quality with a ground loop isolator. Is using a DC-DC converter a good solution? Does it only solve specific problems? Why do some say that it is "overkill"? Thanks for any help you can give!

A badly designed DC-to-DC converter will induce noise.

If you have noise problems insure you have good grounds at both the head end and the amp. Run power to both devices directly from the battery and insure the cable is of a gauge (AWG) suitable for the purpose. Fitting a filter might help but both the Empeg and amp should have filters built-in already.

Use good quality cables between the empeg and amp. Keep them as short as possible to reduce pickup. Do not roll them up at the back of the empeg as it radiates one hell-of-a-lot-of-crap (been there, seen that, done that).

Make sure the connectors on your phone wires are not metal. The shields on these cables are not grounds and should not be shorted together or connected to ground. I used some old good quality cables from a previous project with metal RCA (Phono) plugs and had intermittent bad noise issues because of this.

If you are still having problems go to a good installer and ask them to look at your set-up.