Your speed between the two sites will always be limited by the slowest uplink on either side If one end has fiber and one has cable, you'll be limited to the cable upload speed.
Hardware really doesn't matter in terms of filemaker's needs between those two devices.
You have given us no scope whatsoever about the structure of your two sites, or your need to interconnect them. How many users in each location? How is your filemaker server configured (IE why do you need to connect two sites, rather than hosting at one location?) ? What do you even use filemaker for?
If you give us vague data, you're going to get vague answers.