Hello all,
 
I am looking for some advice on my current situation:
I have a Sennheiser HD 439 at home for my desktop. Good device, nice sound, but I notice when listening to dance music (I listen to a lot of genres, covering the spectrum from metal to dance), I find the "punch" to be lacking just a tiny bit. The cans don't isolate that much, and I have to crank the volume up significantly before either the bass/punch kicks in or before I don't hear my environment anymore(example: I listen to Spotify via phone on wifi, because wired on my laptop Spotify is blocked, and I have to put the volume almost at max before I get the desired sound levels).
I also own a set of Sennheiser CX 175 IEMs which I currently put in my workbag every day and use at work. It happened multiple times I forgot them at home and had to work at the office without any music so I am looking for a pair of headphones I can use at the office. It can be quite noisy sometimes (people talking) so I would prefer some over-ear isolating ones, as well for myself as for other people not needing to hear my music. I do find however that the velour pads of the HD 439 are nice and don't overheat your ears as fast as leather, but I don't know if these pads are one of the reaons they don't isolate that well. The CX 175 offer some more bass and are relatively cheap, but I would prefer a good headphone.
 
TL;DR: I'm looking for advice if I should just buy another set of HD 439's for the office, or if you have any other good recommendations around the same price class (~50 EUR / ~60 USD), or maybe I should buy a DAC or amp or something?

Hey. I recently stepped into dedicated source components and, IMO, they make a huge difference. With my old headphones, ATH M50, it's a different (good!) experience. With your budget, you can look into a few Fiio options. But someone with more experience than me might have some better advice. Good luck

So I've been looking around a bit, and my eye caught the Audio-Technica ATH-M40X.
It's a bit above budget, but I think, according to the reviews, it would be a good replacement for the Sennheiser 439 wit some more punch, but still good flat response.
Any comments?

" I do find however that the velour pads of the HD 439 are nice and don't overheat your ears as fast as leather, but I don't know if these pads are one of the reaons they don't isolate that well. "
 
Yes, the velour earpads add comfort, and also decrease isolation. Some people are more sensitive than others to overheating ears when using headphones that isolate well. I am very sensitive to it, which is why when I need good isolation, and it is safe to have it, I use an IEM that isolates well.