Drum fill cab

Personally I think it's a better idea just to have a loud wedge (eg 15" + 2") and either another 15" or 18" sub underneath.

If you do go for one, you can get away with just two way with twin 15" and a large compression driver or three way by putting a 10" or 12" in the middle.  Don't be tempted to go for a small format (1") compression driver.  You really need the power (and ability to rip the drummers skin off) from a large format compression driver.  As much as I hate to say it, drum fills do not need to sound hi-fi, they just need to reproduce the things the drummer needs to hear loudly!  Singing drummers introduce a whole world of pain into the equation but I'd be persuading any drummer that also sings onto IEM's.  I work with a couple of singing drummers, both use ears and no wedges.

The other alternative is just two large 15"+1.4/2" wedges behind the drummer, then you can use them for any other band members if necessary on other jobs.