I swear by the 350 and have used them for FW
. I would defiantly go with the bio wheel option. The emperor is OK as well, but more filter pads to change and a pair of them would take up most of the space on the back of the tank.
When I had my 75 Gal
set up I used the 350 with 2 bio wheels. Later I added a 250 hot mag as I started to get into Discus.
Depending on the fish load you are planning you can probably start with one filter. If you chose to heavily stock then add more filtration. Cycling the water 10xhour is more of an ideal. I always used 5x as a rule with the more the better.
depending on how you aqua scape remember your water volume is actually going to be something less than 75 gal
Depending on what kind of setup you are planning an undergravel filter with powerheads might be something to investigate to aid you bio filtration. When first getting into the hobby I used this option, but later discarded as I moved into live plants.