I bought another Class D amp and didn't get what I paid for!

A little while back I went on a pleasant drive to purchase a Wyred 4 Sound Class D (ST500) amp rated at 250 watts per channel. When I arrived, I immediately noticed he lived in a small but very nice home on a lake. Anyway he demonstrated that the amp worked fine and I then decided to purchase.
He pulled the amp out and we tried to fit it in its original carton but strangely it wouldn't fit properly. Got it home, plugged it in my second room, sounded pretty good but very powerful. Anyway I decided to try a different set of interconnects on it and that's when I noticed it was the more expensive ST 1000 ( 500 watts per channel), both amps looked identical from the front. But being honest, I call him back and told him you gave me the more expensive ST 1000. This is what he said, Paul I wouldn't of noticed for three months that this occurred and you could of easily kept it with no problems. But since you called me back the same day, we can now make arrangements to exchange it and we did. For a brief moment I thought I could of kept the more expensive amp if I kept my mouth shut but then I quickly realized I did the right thing.

Anyone else have any interesting stories to tell in regards to purchases?