Thanks for the inputs folks....
I have decided to go with the Plantronics DSP 500
It was cheaper than the Sennheiser and has a USB function that the 90 does not.
I need the USB functionality due to the system I am getting has no Mic input when running in surround sound mode (Asus K8v-SE Deluxe).
I think I may have to go with a USB mic as well when running off of the speakers and then having the ability to talk.
Take care:)