So whats my upgrade step?

Currently i have in my main computer (Gaming, acting NAS, music, torrents etc.)

Samsung HD401LJ (100gig Vista 64bit OS, games, programs Drive + 300gig tools, pictures etc)
Western digital WD5000AAKS 1 drive with 500gigs of tv series, recordings other downloads.

While I'm not 100% sure the hard disks are my problem I think it might be a place i can upgrade. I have thought about 2 possible solutions and would like to hear your opinions:

1. buy a velociraptor (450$) and replace the Samsung drive all together.

2. buy another wd5000AAKS (110$) and setup raid0 and also remove the samsung drive.

I have used raid0 a few years ago, but at the time i didn't really have that much hard disk activity to really notice a difference. maybe i do now?

Of course the velociraptor is expensive but i wouldn't mind spending 450$ for 1 drive, but i can't afford 2 velociraptors for raid0 so please don't suggest that :-)

Best regards
Kim