There are some sweet harman kardon speakers that I got to go with my Ipod.
http://www.mobileplanet.com/product....artner=froogle They're mad loud.

As for DJing a party, do you have a PA? (Amp with speakers or self powered speakers?) You really can't use normal computer speakers for that. JBL has some nice self-powered speakers varying in size and price. But, they all use xlr plugs, so you would need a mixer to line the computer into and then like the speakers out of. You might be able to get an adapted that goes 1/8in (computer speaker hole) to 1/4 inch (normal speaker cable) and then get a 1/4 inch to xlr cable, but you'd only be able to use 1 speaker.

I'd say either get nice computer speakers or go to a local DJ/ sound store and ask about buying a PA system. It's really hard to explain online.