looking for a DAC that will add some bottom end

Aragon D2A mkll with its elegant outboard power supply delivers the type of extended forceful bass you are seeking.
Although mine is not yet for sale (hard to part with) there is one for sale from another Audiogon member.
As an extra feature it can properly decode a specially mastered group of 1980's CD's which benefited by having a complementary automatically triggered de-emphasis circuit. It refined the painful digital treble of those early CD's, and is great for those who retained their 1980's CD collection.

Mitcho - I suggest you try some ball bearing type footers and danmping ( sand in bags - or some kind of weight over cloth ) on top of your current DAC first - worth a try
Cheers

If you must try something new the Monarchy Audio M24 or NM24 (new version offering both tube and solid state outputs) are quite good in the bass region.

REL subwoofer.

Bryston BDA-1. The bass you're looking for. But difficult to find used....