You said your old pump is a mag-drive. Are you aware that you may be able to repair it? I've had several mag-drive pumps over the years and the problem is usually with the impeller assembly or just the ceramic shaft. The motors themselves usually don't go bad since they are completely sealed and transfer the energy by magnet through the plastic.
A lot of the time the shaft breaks or wears out which jambs up the impeller. So you think your pump is dead, but it's just a stuck impeller.
Turn the water intake pipe counterclockwise to remove the impeller cover. It's a bayonet mount. The impeller rides on a (usually white) ceramic shaft. On each end of the shaft is a rubber cap and a small nylon washer, so be aware, don't lose them. Sometimes it's a little hard to pull out the impeller due to the magnet built onto it.
If you find any problems with the impeller or shaft, look up your pump online and get a new impeller kit. They are relatively cheap, especially compared to buying a complete pump.
You could also just have some debris stuck in the impeller. Look in the intake pipe to see if there's anything stuck in there.