The panel is painted MDF - would be the perfect wood for these projects if it wouldn't be so damn dusty to work with. :-)
In my first setup I just had one amp with an inline fuse - it was bolted directly to the side of that metal bracket. This current setup needed a bit more space.
One word of advice (from experience) if your battery goes dead: check that your clock, fuel gauge, clutch relay (among other things) all function correctly. My car has a tendency to lock up those functions if the battery goes low and gets boosted. Sometimes it's a good idea to disconnect the battery, get some charge into it, then reconnect and continue charging. That way the car resets itself with a good voltage level. (It isn't the boost, it's the low voltage level that messes it up.)