If it is choppy i would blaim the computer. Maybe a virus checker is running at the same time?
Increase the priority of the software used while streaming. Maybe just "iexplore". Not sure if silverblight shows up as a process. Set them to "Above Normal" and hope they don't get stuck in a loop!
I've noticed that the slight choppiness seems to coincide with Netflix "high-usage" periods, like weekends and evenings. It sometimes smooths out after awhile. The PC is a dual-core with 4GB RAM, RAID array and pretty good video card with HDMI. It should be able to handle Netflix