What is under $5k speaker with best bass slam?

That's easy, get a pair of original Energy 22 Reference Connoisseurs....they easily go down to 25hz and more like 20 without breaking a sweat.

Will 12" drivers produce slam in a 12 by 12 room?

In a room that small, I'd think your biggest problem wouldn't be finding speakers w/ slam, but finding speakers that won't overload the room w/ bass so that it cancels or muddies everything out.

Room modes are going to be a bear in an untreated room of that size. Try this Room Mode Calulator to see how it looks

Nothing beats active bass speakers like Genesis VI or V & Vandersteen V.

Active ATC's are pretty damn impressive for bass slam, but are nowhere near Dh4kim's price range. A guy I bought an amp from had the the SCM 150's and played traditional Japanese and Chinese drum music on them - holy crap!

Explosive dynamics, incredible timbre, and sheer power. Yet, everything was crystal clear.

Doug,

As a fellow drummer, I'll chime in with an opinion. If what you are after is for the low end to be more "lively", then strictly looking for slam capabilities may still leave you wanting. I actually found what I wanted by looking for an extremely balanced and well staged speaker top to bottom. With the midrange especially cleaned up, the stage opened up to the point it was much easier to hear the definition in the low end and it was less of a struggle to follow. I especially want to follow the subtleties of the kick and the baseline and that's what really enabled it for me.

I eventually settled on the ProAC Response 1sc (about $2,500 new, but used on the 'gone for under 2k). They may be too small for a 400 square foot space, but they'd fill a 12 x 12 easily.

Bottom line - if you want to get "involved" with the music and really 'feel' it, you need to be able to hear it clearly. Your milage may vary, but something to think about.