Small holes do look nice but they have a downside when I use them. I tend to have several items that produce heat under the stand and I want that heat to move out the back so I do not enclose it in most cases. A filter drawing 30 watts of power is much the same as a full time 30 watt heater. Add in a few power supplies and other items and you can have more heat than you want setting under the tank full time.
I would say drill two large holes spaced apart the distance you need, then jigsaw from the bottom of the first hole to the bottom of the second hole. Then repeat on the top of the holes.
This is about the easiest and quickest way.
I would use a Forstener bit to avoid tear out when drilling and sandwich a sacrificial piece of wood to the cabinet for the sawing part. Or use a fine tooth blade and put tape on the cut line to reduce tear out there. Or go old school and use a coping saw.
If I had to cut multiples I would make a template to use with a flush trim router after the hole was roughed out.
Dilution is the solution for the pollution.
Quote me as saying I was misquoted.
Once you get rid of integrity the rest is a piece of cake.
Here's to our wives and sweethearts - may they never meet.
If you agreed with me we'd both be right.