The UE phones all have different sound signatures. I went from the 3 to 5 and got more bass, more detail and a bigger soundstage. But the mids were way less forward and the separation is less. The image is not the greatest for rock music. Not the tightest bass and at best uninspiring mids. The 5 pro is better but not in all areas. It is still mid-level for a reason. I think most who go ga-ga over it just haven't hear enough of what is out there. It is a very good earphone not anything really special though. I got my 5 Pro a ways back for $159 shipped from Amazon. For $150 you will get your moneys worth. Having some AKG phones, the mids didn't thrill me and the stiff cable does give trouble esp. in cold weather seasons. No complaints otherwise, just felt I wanted both of what the the 3 and 5 Pro brought to the table with no sacrifice.
So through upgaditis, I bought and sold the 3, 5 Pro, and Triple.fi all within about 3 months. Ended up buying a second SF3 as a backup and used it with my Ety S adapter as my workout phone. It needed the adapter since I found the 3 harsh on the high end and remembered how it became creamy smooth when fed more power. Then the cable upgrade brought a nice SQ boost that put it over the top. The drawbacks are a longer cable, for me UE products still lack in comfort, and they will never isolate like a newer Shure or ETY can(you lose more SQ in noisy environments with UE than the better isolating ones). It is probably still the best sounding universal earphone I have heard though I was not able to A/B compare all the best I have heard.
The SF3 is underutilized and if you have had all three models and amped them, the 3 improves the most. So, I went and used my S adapter and also bought the Westone ES cable for it. The result, In my experience, is a phone with a larger soundstage, more detail, tighter bass, much better mids, better treble, clarity, transparency, comfort, and a bit more speed and impact than a 5 Pro. Cost less also. So, the 5 Pro lost in every way except needing less battery life. Of course this meant I could hear some system noises(button press registering on my iriver) and more hiss(source dependent of course) since of the higher impedance/sensitivity.
I thought the Triple.fi is more extended than a modded three but smaller sounding with the same tips and not near as much fun. Two different signatures though; one is bass oriented and the other balanced with a lean toward the treble end.
I would say for the $125, if you like fast,fun, mid forward, leans toward the bass side of the spectrum signature with a more dynamic-like punch, then modding a SF3 is a real option.
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