I have previously owned the AKG K430's, and for the price I paid I was impressed by the sound quality. The highs and mids came through clearly enough for me (admittedly they're not the most crisp headphones ever, but great for the price I paid of £30), but there was just a little more bass coming through, which I personally like a lot - bass was however far from over the top. The problem with these was the comfort on the top of my head and the general durability. I could cope with wearing them for up to an hour, but there was virtually no padding on the top and it would eventually begin to be literally unbearable around the headband. Comfort around the ears was, however, bearable for a couple of hours, which was fine by me. The problem with durability wasn't the build of the main body of the headphones, as they were strong enough for my use, but it was:
a) the earcups - their coating wore away and now they're just uncoated, thin and vulnerable fabric
b) the cable - it lasted something like two years, but was ruined after that. I understand that the K451s come with two cables, so if one breaks I can just insert another, and if that one also breaks I'm sure I can find an appropriate replacement.
What I'm looking for in my next pair of headphones is something with a slightly more comfortable headband (I understand the K451s come with more substantial padding), a replaceable cable, and good sound, with nice bass response but crisp *enough* mids and highs - I certainly want to be getting pretty crisp mids and highs for a pair of 'phones in their price range. As far as price range goes I think where the K451s stand is where I'm at. I want them to be fairly stylish too.
I thought I ought to ask here as there seem to be very mixed reviews, from "the absolute best for this price" to "the absolute worst for this price", with nowhere in between.
So, after owning the AKG K430s, will I be as pleased with the sound of the K451s (ideally a little more pleased as I'll be paying about £50-£60 rather than £30) but more impressed by the cable/headband-cushioning/earcup-coating?