I am cutting down an oak entertainment center to house a future big screen. Any tips?

Trying to do this without taking it apart?

I would suggest a router, with a guide clamped to the vertical. You can even get router bits that spiral either, or both directions. The advantage of a spiral cut router bit, is that the blade edge is always forcing 'down' into the surface it is cutting, so a bit with the spirals in both directions would give you the cleanest cut on both sides of the surface of the panel. But, even a straight fluted bit will give you a cleaner cut than a circular saw.

If you absolutely must use a circular saw, use a blade with as many teeth as you can get. The more teeth on the blade, the better the finish cut you'll have. Also - go slowly with the saw, so that you are taking smaller 'bites' out of the oak.

Sometimes a piece of tape along the cut will provide enough support to help prevent chipping. To further aid this, you could run a utility knife along the cut line, and score it several times. Again, I would suggest that you use a clamped guide, to run the saw against. (Put the guide below the saw, lol).

Cut from front to back of the unit - you might get just a little blowout as the blade or cutter exits the panel, and it will be easier to hide at the back. To help minimize blowout, you can put a piece of scrap wood against the edge where the blade/cutter will exit the panel.

If you have any questions, or need to talk further about this project, feel free to email me, be happy to help.

Have Fun