I have modded RP-HTX 7 (trough recabling using Canare L2T2S, Canare F-12 Jack, custom ear pads, and some other adjustment)
Just for below 15$ you can make these cans sounded like 150$ ATH-M50. Once it get "tamed" it sounded awesome
http://www.head-fi.org/t/638041/panasonic-rp-htx7-mod-to-the-max
It's also sensitive (sometimes can differ mp3 bitrates and show some small noise from any music). That makes the modded RP-HTX7 good for gaming and music monitoring. Since the modded one has better panning, it helps me a lot at locating enemies (at fps games).
Here's my pitch test result from:
Original thread:
http://www.head-fi.org/t/633360/test-your-ability-to-hear-pitch
Testing page and faq:
http://musicianbrain.com/pitchtest
http://musicianbrain.com/td_faq.htm
I've tried HD 201 and 202 before. These two have muddy sound, good bass, balanced parameters (typical sennheisser headphones).
The downsides is it's sounded "grainy" (which is sounded "cheap" for me) and the built is plastic. IMO, Sennheisser headphone sounded awesome at above 100$ line.
I'll recommend RP-HTX7 or Philips SHP 2700 for cheap budget monitor.
RP-HTX7 has bright and clear sound, cheap for it's quality. The downside of RP-HTX7 is sounded "harsh" and tiring for some people.
(Actually after modding these, I translated the harshness into great detailed treble and nice highs)
SHP 2700 is good at mid and bass. Just for about 30$ (at my country) it's sounded better than 90$ Senn HD series (I forgot the name). The great downside is it's built which can easily broke. (Dunno why Philips gives crappy body for such good driver)....
I think some Beyerdynamic headphones is wise choice too....I've tried 75$ Beyerdynamic DR 231 PRO and it's sounded better than any 80~100$ headphones lines.....