John
As you seem to be the vac expert, which configuration is the most powerful
3 vacs
2 x 6.6 vacs
2 x 8.4 vacs
Cheers
Mark
I like four vacs series/parallel these days buy no point going there as none available to buy ...
There is not a great difference between any two of the better vacs combined , so perhaps pick the machine with the best features for you .
The 8.4 only have about half a HG more suction than the 6.6 , the 8.4 is still a few hundred to buy here but the 6.6 is selling for as little as 99 these days so thats comforting from a replacment point of view .
Also thers no modern designed machine using the 8.4 here yet ...
You should try and test out the various machines available and see which suits you or have the best features
The Enforcer is now also available as a parallel 6.6 two cord so if u came from a high airflow setup a twin 6.6 might feel similar to you . The standard in series Enforcer gives u the option of one cord convience and good heat on cord two .
the Storm ... no one have ever being dissapointed so u can go wrong there
The alltec evolution , some clever combining of heat and good vacs on two cords might meke it a great allrounder .
Its really hard to say which is the best , there is no real standout high performance suction machine available really ,
but most of the better ones available should be good for 100ft using two inch .