A more experienced audiophile told me that my PX-100 is top-of-the-line already and he also advised me to purchase a FiiO amp instead of buying another expensive headphone.
I searched the Internet and found out that there're two FiiO amps available in the market. One of them is the FiiO E5. I liked it better than the other one since it has a rechargeable battery and it's better in quality.
These headphone amplifiers are VERY RARE as only a few true-blooded audiophiles would even think of purchasing one. Most people just spend money on a good or so-so earpiece and that's it. I, on the other hand, wanted something more since I travel a lot and rely on music to prevent me from being bored. I want to hear as little ambient noise as possible so I really searched hard to find one. Good thing I found a local shop (Peeps Game Shop) that sells these babies! I got one for P1.2k. The only disappointment is that they only offer 1-week warranty. They said that I can go back to them in case I need some repairs.
I was blown away by the crisp sounds I heard when I connected the FiiO E5 to my PSP. My PX-100 was vibrating due to the loud bass! I can only hear minimal ambient noise now – which is good!
Whew! No regrets in buying this!!! It's worth the money!!!