1) If I'm only hitting 50% network utilization, I may need a faster landing drive correct?
No. Drive speed is not the issue here. The real issue is your network performance and your desktop network cards. Most desktops sees 300-500mbit/s utilization. Upgrading your network components (nics and switch) to higher grade material will improve your performance substantially (easily 600-900mbit/s). There are a lot of other factors, but drives are very seldom the cause of performance bottlenecks when hard drives are involved.
This is not true. At least not entirely. Yes networks obviously play a role here but drive speed is certainly a factor.
You will get faster network transfer rates when the data being sent over is going to faster drives. If your WHS machine has a variety of drives like mine does you would see this.
On some drives I get a network transfer speed of 60MB/s sustained. If the data goes to a different drive I can get 30MB/s. Hard drives are rated at burst speed but will never get that speed in a sustained transfer. Obviously a gigabit network is capable of higher speeds. It's the drives that are the limiting factor here.