woofers gone wild

Your amp has DC voltage on its output. If the cones move a centimeter this voltage is way more than normal. The amp needs adjustment.

From the pictures I see it looks like a really nice amp for the price. Dare I say DK-like in concept :-)
If the problem is just misadjuctment of the pot to null DC offset it is a real easy fix. In fact, the circuit board may have markings to identify the pot (probably in Italian) and if so you might adjust it yourself. The amp, and your speakers, will sound even better after you correct this problem.

Lousyreeds1...OK, maybe you better have someone who is familiar with electronics look at it. Hopefully it is just a simple adjustment which they might even do for free (if they want your further business).

A "Pot" is a Potentiometer, which is a variable resistor. It consists of a length of conductive material, often in a circle, with high resistance, and a sliding contact so that the length of material which the electricity has to pass through can be changed by moving the slider. Obviously this changes the resistance to the electricity passing through the material. Pots are used in many parts of circuitry, not just volume controls, although that is best known. The typical audio power amp output stage has two transistors, one connected to the (+) power supply, and the other to the (-) power supply. When there is a signal it causes the transistors to conduct, one more and the other less, so that the signal appears at the output. When there is no signal these two transistors should conduct equally, so that the output is neither (+) or (-). Since transistors and other circuitry are not all exactly the same an adjustment pot is provided so that a good balance can be achieved when there is no signal.

I hope this will help you avoid a snow job when you deal with the repairman.

PS: This problem is most often caused by playing too much dissonant music :-)

OK...Forget about the pot. It appears that the Unison amp has an active circuit to balance its output, because other aspects of its circuit design make it particularly prone to DC offset. Something has gone wrong with this circuit, or the DC offset exceeds its correction range and you need someone familiar with the Unison amp to work on it.