The amp in this sale is a good design. If the output section only needs work then I can rebuild it for $280. If the power supply (SMPS) is bad too about $375 for output and power supply rebuild.
If just the outputs are bad it's an easy fix, but the parts are expensive. Only problem for all you DIY'er amp repair guys out there (I see there are quite a few more here now than there were a couple years ago) is that the output drive section, if you are not familiar with the way it works, may cause you some greif and you may blow up lots of expensive outputs over and over again trying to fix this amp yourself.
I would say this amp should do right at 4K. 5K is a MAYBE with higher voltage. It's a chinese prototype, not good enough for Sundown, but maybe good enough for you. I think Jacob should sell it to you guys for $300. Because it's gonna cost you $300 to fix it, and that comes out to about $600-$700 when done, but decent 4K+ amp for $600-$700 aint bad right? It should hold up well after we repair it. Jacob is really hard on amps, I in turn, am REALLY hard on subwoofers. If you have a subwoofer that you claim is indestructable, give it to me for 5 mins... LOL... I'll tear that ***** up. Just like Jacob tore up this amp....