but, beware that submersible pumps add a lot more heat to your tank than external pumps.
I mix my saltwater with a mag 12 because it keeps 40 gallons at about 80 degrees without needing an external heater. If I assume room temp. is 70, thats 10 degrees added to 40 gallons! That's a lot of extra heat.
In my old tank I used 2 sub. pumps, a mag 18 for skimmer, and one mag 12 for return. Since upgrading, and utilizing a Dart w/ manifold, I use none, and have not needed a chiller in 2 years.
I'd imagine you're returning with a submersible also (since you don't want to drill holes.) You may be better off drilling a large enough hole so you could use an external pump to feed your return, your chiller, skimmer and whatever else.
You might actually find that you dont even need a chiller or that you can avoid using one by altering your lighting schedule during the hottest weeks of the year. You wouldnt need a dart, btw. Probably get by with a much smaller pump, ie Iwaki 40.
HTH