Rebuilding a collection

Ok, so i recently moved, and when i moved my laptop and my back up hard drives were stolen out of my car. My laptop had all my music on it that i collected over nearly 7 years. more than 600 gigs, and now that ive replaced the computer i need to rebuild my itunes library, only problem is the sites i used to get my music back when i was downloading it were taken down, and i dont know what i should use.
Anyone with know how would be very welcome