Consider not using a baseboard at all. You get the most rigidity and least vibration with a wall mounted solution. Enlarger and counter top are best to be separated.
It depends on how big the enlarger is, but 3/4 probably isn't thick enough. The factory baseboard of my LPL is at least an inch, and it has a metal stiffener on the bottom.
An alternative, though it's contrary to Ralph's suggestion, would be to mount the enlarger directly to the counter top, with some reinforcement underneath. The completely open surface is nice to work on. Wall mounting accomplishes the same thing, but the manufacturer's wall mounts are usually pretty expensive.
I made my own wall mount fro my Durst L1200, but I'm not sure it was cheaper than buying one. However, it's much more rigid.