For less then $4,000 you can get a used Express, they all have 10 pages of 24 subs.
I've also used an
NSI MC 1616. It's got 16 bump buttons. Cross fade time is controlled by a fader, not programed into the button, but besides that it seems close to what your looking for. For an extra $50 you can get it with
DMX in addition to Microplex.