Lots of scoops and comb filtering...



I think I saw a few Funktion One tops in the last photo as well.
Based on the photos I would say T48's or T36's to hold down the bottom end and DR280's for the tops. If you go with T36's I think the extension would go lower and sound better than the scoop bins that I'm seeing in the photos. Maybe the "dirty" sound you're looking for is the distortion that comes from the front loaded drivers on the scoop bins. The T48's and T36's will sound different because of the filtering inherent in the folded horn design.
As far as amps I would go with any current solid state design. According to most of the articles I've seen on Valve's system they credit their "sound" to creative EQing and a lack of compression/limiting. They leave the source lower and allow for more headroom than the usual guys that run the system on the limiter all night long. In other words; the less you squash the dynamics in the music the better the sound.