ok. i have an80 gig ps3. only used about 20gigs of it. i have a buttload of music, video, etc, i would like to put on it, but i still want room for games (future games i get)

i understand i can only use 2.5" SATA hard drives right? those come up to 750 gigs right? how much would say.. a 250 gb one cost? i have litterally no idea. ive never bought one before.

i have 200 gigs of music and 200 gigs of videos and TV series. thats right 200 gigs of music.. anyways. i would only download a selected list of them. unless its cheaper than i thought.

once i change, will the ps3 have to download anything to the new hard drive to enable me to play games again? like the xmedia crossbar. and stuff? i have an external hard drive i can use to transfer my current stuff.