Well your definetly going to get improved sound not matter which way you go. I would say it depends more on how you want it to look. I personally think the wrx looks good with double dins only. Whether that be the factory radio or an aftermarket. Now I haven't put a clean sweep in a wrx before but they make a factory radio sound AMAZING. Had a lexus rx400 in the shop, we did a clean sweep, Polk speakers all around, 5 ch amp and a sub. It sounded amazing. One of the clearest sounding systems I've ever heard. So if you like the stock look, you will not be dissapointed with the clean sweep.