At $40 for a good submersible, I say just keep saving and get a March pump. Sure, it's another $100, but once you've got it, you're good to go. I use mine for pumping around a single-tier and recirculating ice water through a 25' IC.
The first time I cooled with it, I was thrilled. My tap water is almost 70F, so I can't get too cool with it. I let about 5 gallons trickle through the IC and brought the temp down to 100F. Then I started pumping ice water from my 5 gallon cooler through the IC and back into the cooler. 5 gallons of 100F wort and 5 gallons of 34F water evened out to about 69F in a bit under half an hour. If I'd had another bag of ice, I would have gotten to bed before midnight.
So, I used 10 gallons to cool, and I'm able to find plenty of use for 10 gallons of water.