if you use a siphon, you run the risk of either draining your tank, or overflowing it.
If the power goes out, your siphon will continue to pull water out until the siphon breaks. When the power comes back on, the pump starts pumping water back into the display, but siphons arent meant to start back up automatically. You end up overflowing your tank.
Audisteve, you can buy diamond tipped hole saws on ebay for about $20 including shipping. A guy from china sells em for real cheap. Shipping takes a week or 2 though.