I know a lot of people here collect arcade stuff and often times end up re-wiring f*cking everything in there so I thought I'd mention this:
You can get it on Amazon for $22.For some reason
CNet reviewed it, which is how I came to know that it even exists.

Its pretty simple as far as hookups go. It has stereo RCAs and a 1/8 stereo jack. There is nothing "digital" about it, despite the name. It only has line-level inputs.
It says its 20W. I hooked it up in place of my vintage Marantz in the living room and I'd say that's probably right. Its absolutely loud enough for any arcade machine use. Its also small, comes with its own power supply, and easily mountable.
There is a tone bypass switch on it, which is kind of odd. It bypasses the bass/treble knobs. I suggest using it and just letting it run flat. Arcade machines usually have a flattish tone anyway, and the tone circuit in this thing is garbage.
As an amp, audio quality-wise, its nothing to get excited about. Not great, not terrible. No highs, few lows, could almost be Bose.

Its 22 friggn dollars though, so its basically a miracle. Use it in whatever project you'd like. You could even use it for a stereo if your standards aren't very high. Maybe for your garage or whatever.