I agree with both posts.
If you are going to just mix music as a DJ try
http://www.atomixmp3.com/download.html
It's simple but I did a whole impromtu party with MP3's on it while I was in Chicago over the holidays! Make sure you get 2 soundblaster cards which makes it easier to use. Steinberg also has a new program called Traktor which is good. Both are very commercial but it gets the job done.
If you are looking to sample I actually use Recycle when on the road on my laptop.!
It's at;
http://www.propellerheads.se/
If you are trying to make music Pro-Tools in all its forms is the best. If you have a lump of cash grab their mix desk and a dual cpu g4. I did a whole album on that!
Check out all the Pro-Tools lines;
http://www.digidesign.com
Also go to
http://www.emusician.com to check out the new hot programs that we don't know about or haven't used yet!