If you're planning on paint, mdf, or better yet sign board mdf can be perfect. Sign board takes paint really well.
Painted pine generally looks bad unless you fill, seal and sand reseal, and sand again.
On a stand that size, if you plan to skin with plywood, a decent veneer really doesn't cost that much more than good birch plywood.
If you aren't experienced with door hanging, consider skipping hinges or having a cabinet shop make the doors and install the hinges for you. If you are willing to let them do it in slack time, the cost won't be a bad as you might think. Learning on a huge piece of furniture you will be looking at every day isn't usually a good thing.
Don't forget to install a good power strip setup inside the stand. I like this one http://www.amazon.com/Belkin-F5H300-.../dp/B00006BB7U
Ten outlets and a fifteen foot cord.