yeah , the mytee would not be quite as powerfull as two magmas ... that would be about 23amps ... the mytee twin would be about 20 amps .
I can still put my other heater with the new one for 26 amps ( still have to try that )
You have to consider whats practical to plug into the house also .
If you come across another lower-powered heater used perhaps .... i would put that with your magma , should be plenty .