Found this deal a couple months ago and grabbed 4 myself.
VMInnovations has the Polk Audio PAD2000.2 two channel class D amps for $54.99. Use the coupon code "DealNews5Off" for a additional 5% discount. They've actually gone up a few bucks so, be aware of that.
Amp is rated 2 x 125 watts @ 4 ohms stereo, 2 x 250 @ 2 ohm stereo. 500 watts @ 4 bridged. Because it's a two channel amp there is no subsonic filter but, it does offer a frequency multiplier switch
Rob "HiFi" Vega tested one and got 589 watts at 4 ohms bridged. The video is linked below. I am personally using one on a couple of IDQ DVC V2 10's in my daily driver and it sounds great.
These amps seem to be clones of the PPI Phantom P600.2 and Soundstream TN2.600d.
Polk Audio PAD2000.2
They are also listed on eBay so, you might get lucky with a discount code there as well.
Rob "HiFi" Vega's dyno test