I have both IEMs and I've found that SE535 has a considerably more amount of bass and sound really full and warm, but the 425 still does have a punchy bass.
425 has amazing attack speed when I listened to strings and Lang Lang playing piano.
Both have the detachable cable and you can buy them anytime pretty much I believe it's around $40~50
I don't listen to a lot of bass heavy songs but I don't believe neither would be muddled without EQ
Both the metallic case and clear case are really cheaply made I have to admit and I was really disappointed (so all in all it doesn't really matter just go for the ones you like)
The cables are like a tank, one of the nicest cables - no microphonics, kevlar reinforced, memory wire
BTW: the clear cables aren't really that clear, you can see the silver/copper colored strands inside and after some usage they seem have dulled in luster
Hope this helps ask any more questions if you have any!