Hi, so I'm getting my first more-than-$10 headphones (a pair of Sennheiser HD 429 S) and if I really like the sound I'm planning on buying a second pair for home use (Since the HD are meant for my smartphone) at around $150, I listen to christian music so that translates to a lot of genres, but mainly rock, ballads and ocassional electronical (i think it's called dubstep in the US) When I listen to rock and dubstep I really apreciate a lot of bass but I would also like stunning clarity in the sound and being able to pick up all the instruments and all that, I've heard lots of good things about the ATH M50s, are they my best bet? These would be meant to use without an amp for now.
Headphones around $150
Grados make rock (really all treble-based music: organ and chamber music) sound amazing. They're bright though, so piano doesn't sound right to me. SR125i is the dud amongst the SR series. I would choose SR225i or 60/80i. They don't have the bass for dance music. This can be improved somewhat by using tape modded L-cushions.
I haven't heard AD700x. If you're consider open models, DT990 works for your genres. It has enough bass for dance and enough treble for rock.
125 sounds less like 225 than 80 does because there's a trough in the treble from 2.5 to 5 kHz (that red dip at the point where blue and green spike). We are most sensitive to treble in the 2-4 kHz range so we notice that sudden dip. You can see how close 80 and 225 look, and they sound similar. 60 has a dip too, but it has other worthwhile characteristics such as having more bass which makes it the most balanced. 125 just has nothing going for it compared to the others.