I have an 06 Si and have been asking myself the same thing. The conclusion I have come to is that if you want under 275 hp you can s/c but at a price of over 4000.00 for the comptech kit for only a 50-75 hp gain I dont think its worth it. For a little more than that you can buy the kit hytech is putting together that includes cams, valves, retainers, pistons, header, exhaust and reflash that is supposed to make over 250 whp. So for a little more than the comptech kit you get almost the same peak power but you are still n/a. But f you want 280 or more whp turbo is the way to go. The ajp kit is making in the 350 range on stock internals and that kit is in the 5000 range. So first decide how much power you want then we can get into the detail of whats the best way to make it.