Could use more of a breakdown of what your uses are, but heres some recommendations:
2.1
Altec Lansing MX5021: Should be pretty good for music, midrange is more defined that most speakers (Logitech). Goes for about $150 Canadian, but may be more difficult to find now.
Logitech Z-2300: Best value. Personally owned these for half a year. Their midrange is very lacking, soundstage stinks unless you use CMS3D, which distorts sound. However, this is probably true for a majority of computer speakers. Bass is very nice, but a bit boomy depending on your placement (I practically rode the woofer with it taking up my leg room under desk). Still, in terms of price and performance, it's good. Could be found for $80 CDN.
Klipsch Promedia 2.1: Considered one of, if not the best in terms of quality. Bass and midrange should be among the best for computer speakers. Blah, why am I trying to sell them, you've owned Klipschs

. They are on the expensive side though, $219 here is the best they go for.
5.1
Logitech Z-5300: They're 5.1, quality isn't exactly the best, but they are better than budget speakers, and you can get 5 for $150-ish. Could probably compare them to the Z-2300s. Great for games and movies.
Logitech Z-5500: Big step from 5300s, a lot of people rave about theri quality, I almost ordered them a month ago (went to order confirmation, but cancelled, thank god, due to Dell's screw up). Has a built in Decoder on the control pod. It's among the best in terms of popularity with computer speakers. Same issues with all Logitech speakers here, lots of flash, boomy bass and no mid-range. Again, great for games and movies.
That's about it for speakers in your budget range. You could always go with bookshelves with great frequency responce, hueg sound stage, accurracy and upgradability. However, the price of the receiver will kill you. If you do consider it, you could check out Best Buy's Insignia Line for really cheap speakers that are actually pretty good, and a really cheap Insignia receiver or amp that works; all should be less than $150 for a 2.0 setup. You may even be able to get a 4.0 going for your budget. Good luck.