[Gooserider]

Yeah, either the site or my browser was acting up last night, kept giving me 'unable to connect' messages, and I'd keep hitting the post reply button each time (I generally use the quick reply box) and eventually it would go through. I guess it was getting in some times but not posting back to me.

In terms of the box, your engineer friend is probably right from a theoretical standpoint, the products suggested are very good. (BTW, have you checked w/ McMaster Carr for them?) but may not be practical from either a cost standpoint or just that us mere mortals can't find anyplace to purchase them.

I also spend a lot of time over at Silent PC Review (SPCR.com) where there is a great deal of interest in this sort of material, and a great deal of experimenting with 'poor man' solutions using more readily available material. Personally I've found aluminum faced asphalt roofers tape is great for killing case resonance (Probably not an issue with your box) and have seen lots of good reports on the use of rebond foam carpet padding as a sound absorber in cases where space is limited. The combo is said to compare well to Acoustipak at a fraction of the cost. In the case of your box (which I think many over on SPCR would love BTW) I would probably go with 1" thick egg crate foam tiles (available for ~ $1.oo each on E-bay) for the baffle lining, and sorbothane rubber (from McMaster Carr) for the pump isolation.

Gooserider