How much can a leaking storage cap degrade music?

My amp appears to to have a leaking storage cap. The only obvious problem visible to me. My music sounds horrible now.
The amp is a Parasound HCA 1000a. The cap in question has a thin oily film on it where-as the other 3 are dry.
If it's leaked it's electrolyte, it no longer has it's rated capacitance(may be completely open), and the amp will have lost it's dynamics. I would replace all four of the power supply's 10,000mF caps at the same time, to avoid further problems.