To be honest the actual hard disk probably won't make much difference. I use a boggo WD hard disk and it is fine.
Of more importance is the transfer protocol you use - I would certainly consider setting up a LAN box (NAS storage) if you have more than one machine on a network, or Firewire / E-SATA if you don't.
The point is that doing any serious copying to / from a USB2 drive of that size will take ages. Eg what are you planning to do about backing it all up ?
Also I think you will find that MP3 files will keep enough musical detail if you set them at a high bitrate, eg above 256K. I certainly can't hear the difference. This then gives you better options in terns of cataloging your music collection , as you get to keep all the track info which will be created from the CD lookup info when you rip. If you are individually naming wav files and trying to catalog them as you go, I think you will make a rod for your own back.
Just a thought.