KSC75 is a clip on headphone... soundmagic is a iem... philips... i think is iem... u r comparing diff stuffs lar... ^^ u mean in terms of SQ? budget? or headphone? iem? ^^

KSC75 got high praise for being a bang for a buck earphones by not only locals but also head-fiers, but couple of things about clip ons is the sound leakage and also there have been ppl who are not really comfortable using it especially ppl who wear glasses.... but if u can compromise that, then it should be ur choice...

PL21 is for me considered a really balance earphones with a good build... SQ wise for me its really good compare to my stock iphone earbuds. good amount of bass but not lacking clarity and details. also considered a bang for bucks...

as for philips SHE9700 i never audition it, but from my experience, philips earphone usually got quantity bass that will satisfy u and a fun sounding phones (im comparing it with my philips buds, and yes it satisfy my needs for music)
so hope with this explanation, u can make some conclusions and be happy with what u'll going to get...