Why not get a top end porty? They will have similar performance to an electric tm and probably cheaper to buy and maintain.
They say a PD blower doesn't loose as much cfm/lift under restriction as electric vacs ...
A 5HP electric motor on a 33 blower would have only about 10hg and 160 cfm compared to an airflex Storm which has 9hg and up to 290 cfm .
But under working conditions , where the wand meets the carpet , its said the electric vacs performance dips below that of the blower based system .
Just stating what iv read , its difficult to measure ... i think the guys on TMF have come up with a sophisticated test ... the 5 gallon bucket test ! after 100ft of hose dip the hose in the bucket of water and measure time to empty .
Having said that ,iv read that mytee tested a 5hp pd blower etm and concluded that their electric vac etm ( i presume they mean the quad version ) gave better vacuum . But there could be more to that also , cost to produce , shipping weight etc ..