I just did this DIY today and I noticed a huge improvement. I bought some 65W h9 bulbs from ebay (around $15 w/shipping) just to test the mod before I spend some money on a quality set of bulbs. Also I currently own a 13' wrx. Sorry in advance for the poor quality cell phone pics. The install took about 20 minutes, def a must do DIY.
Another shot (you can tell the difference by looking at the OEM fog bulb):
Also here is a shot of some yellow DRL bulbs I also installed. I def love the yellow look: