In my opinion the only reason to keep the stock intake is to save money, so with that line of thinking I would go for the cheapest filter until you can afford a real airbox. The stock one is Horrible. If you're purely looking at filters for filtration, a Donaldson AIS is the way to go. Best bang for the buck is a Tymar. Best all around is AFE2. I belive afe makes a stock replacement with proguard7, but I wouldnt waste money on a stock box, theryre a bad design, IMO.