I am also a big fan of the Mianne benchwork. Very nice, well made, good quality and goes together quickly and easily, all with no mess! I also did just what you are suggesting for the plywood, had the home center cut it all to size for me.
Mianne is also quite versatile if you ever want to add on or make any changes. I've ordered a few more things from them and added on to my original benchwork. And as GRJ said above, they also provide detailed instructions and drawings of how to assemble it.
