I bought the Amp last year around this time for $25.
It is not the world's best set of speakers, and they're also not the world's loudest speakers. Cranking the PSP to max and the Amp to max, you'll still have trouble hearing the PSP in a noisy room.
However, they are a great set of travel speakers. They fold up nicely, they come in a zippered case that holds the folded amp and all the cables and power supply.
I use them as the speakers for my keyboard -- they perch nicely right atop the keyboard and deliver a good sound, much better than the buzzy flat speakers I had before and they are light and have a small footprint. I wish they delivered a bit more of a deeper, louder sound. But their convenience, portability, and high degree of usability make up for that.
I also use them when I need to play something (on the PSP or my mp3 player) for others to hear. You can hear it well in a good sized room if there's not a lot of background noise.
You can use AC or 4 AAA batteries, which is also nice for the times you have a power source and times you don't.
