I'm not sure who gave you the figure of $300, but your circ pump
retails for about 1/2 that...
Nothing wrong in using a different pump, but be aware of a few things... Continuous 24 hr duty on a circ pump generates alot of heat, be sure your pump is meant to run 24 hours a day, 365 days a year...in a setting where ambient temp will already be over 100 F, you won't get much use out of a pump that is designed for intermittant applications.
Also, Hot tub water is, by nature, a very harsh environment for any peice of equipment... Your current pump is magnetically driven (no shaft, ie no shaft seals to leak)... you'll want to keep a close eye on your H2O chemistry if you're going with a traditional design pump, shaft seal leaks will ruin a pump like this in no time....
When working properly, your current pump pulls about 0.6 amps, and flows approx 3 g/min. It is a water cooled design, transfering nearly all the heat it generates back into the spa (The magnetically designed pump allows the front of the motor to double as the rear of the wet-end) Frankly, I think you'll go through more than 3 of these other pumps before going through another Silentflo 5000.
It appears your choice for replacement draws about double the amps, is meant for intermittant use, will not transfer much heat back into the water (The largest part of your elec. bill in ownership of a spa), and will run extrtemely hot.
Hope this info is helpfull, probably not what you want to hear
