When I transfer files to my Netgear Stora, I generally get between ~500-1000kbps.
It appears to be a known problem.
Do any NAS exist which can copy at a faster rate?
I would recommand this awesome website: http://www.smallnetbuilder.com And more specifically: http://www.smallnetbuilder.com/component/option,com_nas/Itemid,190
All the answer for NAS are around there
However, the speed is limited by several factors:
Hope it helps