Kenwood KAC-8452 volume fluctuations

I recently got my first system installed: -Kenwood 180W HU -Infinity Kappa 682.7cf 5x7s in front (100W RMS @ 2 ohm) -Kenwood 5x7 somethings in rear (50W RMS I think) -Kenwood 8452 4/3/2 channel amp -Infinity Reference 1050W 10" sub (250W RMS @ 4 ohm) I have the front Infinities and the sub powered off the amp, so it's doing 100W RMSx2 @ 2 ohm and 200W RMSx1 @ 4 ohm bridged. The amp's crossover is set up to send high notes to the front and lows to the sub, and bass boost is turned on (all of this is described in the manual). If I play my music anywhere about about half volume (not very loud) it starts fluctuation. It will down for a while, then back up, then back down for longer. One time I was blasting for about an hour straight and it just shut off, I touched the amp and it was burning hot. I've noticed this happens more with rock than hip-hop, so I'm assuming the 2 ohm speakers are pulling a lot of current and heating up the amp, but it will happen with rock. Since installing, I've switched to a Dual deck with the motorized faceplate and mp3 capability, and the problem is the same. I've also gotten some brackets to mount the amp about an inch and a half off of the box, and I'll fold down my rear seats so the amp is in open air, but nothing helps. The box it's in now is only temporary and I'm building a nice custom one, what can I do to promote better cooling so that I'm not embarrassed by my system changing its own volume all the time?

Was it installed by a shop or by yourself? So the infinity  speakers have a 2 ohm voice coil? Are your sure the front channel of the amp or the one you are using is 2 ohm stable per channel, if not this could be a problem ie heat up and shut down. You switched from a Kenwood head unit to a Dual? Thats quite a slide down the quality scale...I am also not a fan of running the bass boost, generaly it misconcieved that this actually put more power to the sub. I've found this usually leads tot he sub being over-driven into distortion. I

Well the Kenwood is a few years old and occasionally has problems spitting out CDs, I got the Dual at Wal-Mart for $30 (happened to show up during a 75% off clearance sale), and I like the motorized face, remote, volume 'knob' instead of buttons, and mp3 capability. I talked to a friend of mine who does car audio/customization stuff for a living and he said Dual gets a bad rap because it's cheap, but it's not that bad. I'd never use Dual subs though, they're absolute garbage. Yes, I'm positive the amp is 2 ohm stable. Here's the user's manual: Link Page 7 confirms it's 2 ohm stable, and I used the configuration recommended on the middle left of page 6. I can turn the volume most of the way up without getting any distortion, everything is extremely clean and clear, which is what I was going for with this setup, but I just can't have it loud for too long. Would I be better off dropping down to some 4 ohm speakers? It'd be a real hassle to sell these and install new ones, but if it's the only solution to this stupid problem I guess I'd do it.

Forgot to mention; I installed it all myself. Four gauge power and ground wire all the way, 12 gauge speaker wire, good, shielded RCA cables from the HU to the amp.