+1 to Drilling > External Overflow
Best bet is to really take your time, and drill it. This way you are forced to put a sump on and gather the equipment you may want. If you are up for it, you can drill it yourself as it's kind of fun.
I'm running a "herbie" overflow and it is pretty quiet. Kind of annoying to get it dialed in, but seems like a pretty straight forward and simple design.
There is always a few ways to skin a cat
