http://soundcloud.com/geoffhodsman/kickportdemoFor the longest time I had basically no reso head on the kick, but I put the ported Evans head back on to mount the Kickport, and damned if it didn't sound better already.
The Kickport is pretty gnar though. Maybe a bit subtle in the clip I posted but I can certainly 'feel' the difference. It is a bit easier to do my double strokes, I guess the head is bouncing better. Also it just generally feels like the kick drum is more powerful.
I recorded by just putting one of my AT2020s five feet in front of the kit.
Listening to the clip, I feel like there is a lot more focus on a specific low frequency, as opposed to a big mix of frequency peaks from low to low mid, and the punch is more pronounced. So basically it sounds closer to what one might morph their kick into in their DAW.