Blackened Cap inside amp...Is this a problem?

I'd say it's probably fine as long as the solder joints are still good and the capacitor is not damaged under the PCB (be very careful and verify the capacitors aren't charged if you want to unscrew the PCB to check that - probably a good idea if you're comfortable doing so). You could try cleaning some of the crap with isopropyl (preferably denatured, but at the very least, 90%+) or acetone. Looks like there is flux on those PCBs that was never cleaned off...

What kind of capacitors are they?

What's on the other side of that board? Looks like a 1 watt resistor or something. I would take that board off and turn it over to check that part for value and replace if out of spec.

Wow, I totally missed that before. Eyesightfail, LOL. Unplug that board (again, make sure the caps are discharged, put a 1k resistor across the poles for a few minutes otherwise) and make sure the resistor isn't burned and measure that resistor with an ohmmeter and make sure it's not open and that it's at least close to the rated value. Replace if necessary. And check to see if any electrolyte is leaking or anything on the cap. They all seem ok from "here" though. I'd say measure the capacitance but you probably don't have an LCR meter so you can skip that.