Welcome to the Addiction.... I used to Live in Vegas (Summerlin)......
Honestly for $100 you are gonna be stuck buying an cheap set off of Ebay.... Here is what you do. go to your local pawn shop and buy something really cheap (Or the Ebay ones) this is only if you do not have a basic sound setup right now. Get something inexpensive and start saving for a decent set of Monitors..... When it comes to sound creation you want to make sure you have quality equipment.
Save ya money and get the right thing the first time, or at least get as close as possible without over extending yourself.
I am currently using the speaker system I got for my CPU..... It is not bad, but it is not desigend for what I am using it for, therefore some of the sounds are not true.....
You could also take that $100 bucks and invest in a good set of headphones. I use mine more than a little bit. At this point I would be more inclined to spend the money that way.....
But for the hell of it, here is a link to some inexpensive versions you may want to review..... Read the reviews and do some research.... You may get lucky and find a set at a great price and have wonderful quality.....
http://www.zzounds.com/cat--Desktop-Mul ... tors--2866
As stated above, alot of this depends on what you expect from them.... That price range is very limiting..... I would not spend less than $300 on a set if I had to have some, because that price range for the pair is where you start to get into decent quality stuff....... But there are some inexpensiv ones to get.....
BUt in most cases you get what you pay for.........