I agree with RehabMan, the two biggest culprits here are 1- the network performance; 2- drive extender. A combination of the two is the reason I never used WHS for more than backups.
For the network performance there are quite a few tweaks you can do but WHS is still limited to SMBv1 so file share performance will always be mediocre.
When you do get around to looking at new hardware. I can highly recommend the [url=http://www.supermicro.com/products/nfo/atom.cfm#MB]Supermicro Atom motherboards[/url]. They all have dual Intel NICs, IPMI 2.0 and typically at least 6 SATA ports. I have three of them running at home.
The Intel Atom D510, Intel Atom D525 and AMD Zacate will be your goto Vail processors.
