I personally like the idea of the notebook drive. My HTPC has the WD 1TB green drive and I think its still too loud. I've considered getting a notebook drive or SSD for the OS/apps and use the 1TB drive exclusively for media. The 7200 rpm notebook drives aren't too sluggish IMO. Have you considered SSD's?
Also, theres a 45W Athlon 5050e out there that's a little faster than the 4850e. For some reason newegg doesn't carry it, but other sites (mwave, directron, tigerdirect) do.