I know. The Russian review is pretty good, but google translate is not very good at translating. The most important part of review is the table with the measurement summary. For example, in the case with Kenwood XR-4S everything looks pretty good, the RMS wattage, THD, noise, and channel separation. The only strange thing was the frequency response (0db/-1dB) band is "only" 11 — 18400Hz. I could live with that "limitation" (my ear can't hear 20KHz at all) for the price. The interesting thing is that the amplifier did not get warm enough during the tests to turn on the internal fan. The Polk D5000.5 review was a bit more thorough because it involved a listening test.
I don't understand the 8 gauge comment. Does the Polk amplifier accept only 8 gauge wire? I didn't think so. Anyways, I own a PPI P800.4, which is supposed to be very similar to Polk D4000.4, and it does accept 4 gauge. I think they're the same design, down to the circuit board and the controls/connectors side plates. I wouldn't run 8 gauge wire all the way from the battery, but I would have no problem with running 2-ft long 8 gauge wire from the distribution block to the amplifier. However, 8 gauge should not be necessary in this case.