How many times is a perceived problem, just operator error?
If the problem is bad sound then: always.
Speaking of operator error, you just cleaned. Good. But did you take apart and clean all the connections? Anything more than a few months and you will be amazed what an improvement it will make. There's a million products but even just ordinary alcohol on a clean cloth- which is in fact what Keith Herron recommends. Clean all the AC plugs, speaker and cable terminals, RCAs- everything you can get at where metal contacts metal.
Now for putting it back together. Do your best to keep everything away from everything else. Absolutely avoid coiling AC cords or having anything with signal running parallel to anything else, especially AC.
Try and get everything up off the floor. Even an inch is an improvement. Ceramic insulators are best but wood blocks are convenient and really anything will be better than on the floor. If its just not possible then let AC lay on the floor but get those interconnects and speaker cable up!
If its been more than a year since you've done this, or especially if like most audiophiles you never have, ever, then I can guarantee you will hear improvement like if you spent a couple grand on new gear.
This is why I say: always. You've been operating in error, and didn't even know it.