how to have a quiet set up? foam under sump?

[sphelps]

Drain noise will be eliminated by a herbie system, provided it's done properly. Vibration will source from your pumps, mainly the return pump but also the skimmer pump as well. Trying to rely on vibration pads or anything of that nature will ultimately deem unsuccessful. What you need are low vibration pumps, the tank is small enough to use a relatively small return pump so going with something like an ehiem will likely be quite enough. With skimmers however you tend to pay more for something quiet, not only in vibration but in air suction noise as well.

Also just to note if you seal up your cabinet to insulate sound you'll also prevent air circulation which will result in mold growth so the key is really to eliminate the noise by using quality equipment or relocate the sump.