I have been using UE 200s for a while now and I want an upgrade under 100$. I really like the look of the silver Metrofi and UE 500. I can afford the UE 600s but if it is not too much better than the other two than I would prefer to save my money and get what's cheaper. I mainly want to know which of the two silver buds are better. 550s? Or Metrofi 220s.

I don't care about comfort and fit too much. I like the punchy bass and nice highs on the 200s but I am looking for more mids and a little bit more bass. I want clear vocals and clear highs. I am open to other suggestions that are also under 100$.

The Sony EX510 offers very clean, clear, detailed sound in mids, highs and bass (deep, punchy) with wide soundstage. The HF5 are amazing if you are looking for clear, detailed mids, extended highs and good punchy bass with deep tight inear seal. The both worth the price(upgrade) over UE200, one (HF5) is hyper detailed in mids n highs with good bass response and other (EX510) is wide, open, clean, warm and fun to listen with deep punchy bass.

I know its quite some time since you asked this question, but my apologies I only saw this thread today... I own both the 500 and the 600 and i must say the bass on the 500 is really smooth and dynamic, a little punchy but not as strong as the higher end ones like ue700 or triple fi 10.  The 600s lacked a bit in bass. It's flatter. But clarity wise, it was an epic ownage. I heard things in my music i never heard in my 500s. I could tell which song in my iPod music library was a rip-off from radio as i can hear the radio static very clearly. So, bass is for the 500, clarity is for the 600. I do not know which one i prefer.. I still keep both pairs. When i feel like it i switch to the other pair. So perhaps you would make your own decision which one you would prefer?
side note, my 500's 'ue' logo and right-left indicators came off very quickly (some already came off on the first day) but not on the 600. I also experienced driver flex on one ear on the 500. Maybe i received a faulty pair. Replacing it soon. Both IEMs do burn in. I could hear the difference.