Alright thanks dude, currently figuring out which is the best headphone to get first and which will suit my daily life the most.
If you are using them in a shared office environment, closed back is probably the way to go if you want more breadth of sound then most IEMs are going to provide. I don't mind a good set of IEMs but they can be uncomfortable to me for long periods and you can get some seriously nice cans by the time you start talking about CIEMs.
My current regulars are:
Hifiman HE4xx from Massdrop (open Planars)
Massdrop X Nuforce EDC (IEMs)
AKG K545 (closed back)
Koss Pro DJ200 (closed back)
The Koss were some of my first cans and while they don't sound near as good as my AKG they are a great pair that can handle a beating. I swapped the ear pads on them for some M50 'leather' pads I purchased, which helped with sound isolation and comfort. They are not a bad can if you can still find them for less than the 100USD.
Really, I think you need to answer three questions:
1. What will your source device(s) be? This will determine how much impedance your phones can really be.
2. What are your listening environments like? This will likely answer the open vs. closed question
3. How portable do you want to be? This will determine size. Some cans will be pretty portable, others won't. IEMs can really go anywhere.