the difference is ...
the 1200w has 112 " lift ( suction )
the 1400w has 137 " lift
Cfm is almost the same for both at 95
the 1200w draws about 5.5 amps
the 1500w draws about 7 amps
why do they use the 1200 as standard ? perhaps they are being cautious or strictly adhering to electrical product standards ... but two of the 1400w will be fine in practice , combined with your pump( 1 amp ) there will be around 15 amps max on the cord although this will fluctuate downwards during use ... worst that can happen is a slightly warmer plug on extended use than with the less powerful vacs ... other manufactures use the twin 1400w + pump on one cord so its fine .
pump wise , apart from the regular sureflo ect ... prochem seem to be fitting a nice , 150 psi surflo induction pump which is available on ebay .
Accessory planet has the american aquatec pumps up to 220psi
The ametek premium vacs on ebay for 55 are made in the ametek european plants .... the lamb ameteks at twice that price are made in the Mexican plant