Don't cut the board, chances are that it's a load bearing support so if you cut it, down goes the tank. I had a similar problem with my old stand, I ended up building a custom stand to enable me to have a sump. I'd look into doing that, there are plenty of ideas over in the DIY forums.
"If your wife ever asks how much something was for your tank, just tell her you got it on sale and you had to have it! She'll understand"