Dont spend a lot of money on headphones. For example: Panasonic RP-TCM125 for 15-20 bucks is going to match anything under a hundred bucks. Why: its a good implementation of a dynamic driver (which is what all these sub-100 buck headphones use and many up to 200 actually) It also has about as good noise isolation as anything else in that price point.
Beyond that Panasonic for example, there is no sound quality improvement to be had until you crack about $125 and you step up to for example Etymotic HF3, which uses balanced armature and is actually a proper step up in sound from the 20 bucks.
So if you are going to ditch the stock headset, just be careful not to waste more money. The main improvement you wlll get on the stock headset is not sound quality but noise seal and fit that actually stays in your ears. And that you can do for 20 bucks.
IMO basically at best you have a 20 buck headset and you spent and extra 30 on the Bose brand. Am not singling out Bose, like many out there Sony for example does the same with their many overpriced headsets that use dynamic drivers....but at least Sony also offers a 20 buck headset that just will about perform the same that Panasonic will do.
So if you dont want to spend $125, personally I wouldnt go past the 20 buck mark. You can match sound quality of any sub $100 headphones for that little. All those ones in between are basically a ripoff.
