Generally any of the mufflers (Soffit, Joist or DV) will add a lot of resistance to the line and so require an in-line fan to compensate
Ahh! Now it makes sense....... I was thinking that the fan was just for moving air..... Never occurred to me that it's helping to compensate for the added resistance. Didn't even think that there was resistance, but makes 100% sense that there would be.
Hopefully time will pass quickly so we can get started in the next couple months, and figure out budget and stuff.
Thanks again to everyone who has commented and made suggestions as well. I'll hopefully get a build thread up when things get started.