I have decided to go with what everyone calls "hardboard." The cabinet itself is pine stained with a mild green. But its 18" deep and I think thats back far enough that the hardboard wont really be seen. Plus the stereo stuff will be in front of it.
I learn now that next time ill buy plywood from a respectable place and get a quality face instead of pine.
The back of the box is about 6" from the wall, so its pretty tight. Thats also why im going with hardboard. Easier to assemble I am betting.
Thanks for the advice.