Thanks for the tip... I called the fella who runs that site, and he was very helpful. it looks like his product could satisfy my needs... I might could even put a large vent over the intry door to get the rest of the square inches of area I need.
He also mentioned another product... smartvent... they have an "engineered" area similar to the above product, that is even larger than the actual LxW square inches (200 in^2 per vent). nice thing is, they will fit into my existing holes, unlike the above product... mad thing is they are like $200 each (and I need 7). anybody know of a similar, but less expensive product than the smartvents?