The more hard drives you have the higher the transfer speed with larger files, as the large file is split across multiple hard drives. Each hard drive can then serve up its chuck of the file at the same time, giving good transfer speeds.
But with lots of small files you will not see much benefit. Servers do not like transferring lots of small files as there is an overhead associated with each, which slows it down.
For example:
I copied from the server to the local PC a collection of about 2,000 files totalling 1GB in size, this tranferred at about 55mbits on the first run, about 75mbits on the second run, this was due to the server caching the files in memory so not having to load them off a slower hard drive.
I then copied from the server to the local PC a single contigious file totalling 1GB in size, this tranffered at about 115mbits on the first run and the same on the second run. This was hitting 98% utilization on the gigabit network card.
The actual transfer rate will vary with the size of the files you are moving
If the PC you transferring to has a SSD hard drive and large amount of RAM you will see greater transfer rates. The transfer rate is affected by the speed of source and destination hard disks.