I researched many amps just recently. I was looking for a 4 channel cheap amp but enough power if I wanted to upgrade the stock speakers.
I came up with a Pioneer 300W 4-channel amp. for $99 and it was not from eBay.

Most of the 4 channel low cost amps I was looking for were actually over priced or had bad reviews about them. I ended up choosing one of those electric dot com warehouses. I've been happy so far. No external noises at all.