1. Another question I would ask since you know know your stuff, would there be a huge difference between a closed back and an open backed headphone when trying to get an accurate true mix?
2. I'm planning on possibly building a real home studio in the future but for the moment I'm producing in a make shift non sound proof area since I use all digital tools and samples it's not a problem yet.... I'm just wondering if I'll be hearing the sound from the TV in the living room of my house that always seems to be on due to my roommates with the open backed headphones, but I also don't wanna sacrifice quality....
3. How important is it to have open backed vs closed backed? considering basses and 808's and punchy kicks seem to be my problem.
4. Obviously I would like to do as little compensating and eqing as possible after listening on other systems
1. Full-size closed headphones also have a tendency to have bass build up in the cup which may be something you want to avoid since it isn't a true representation of your mix.
2. Yes there will be a difference, obviously in sound isolation for one. Semi-open or open headphones will let you hear noises from the outside as well as anyone close to you will hear your headphones. However as stated in the post by Aizura semi-open and open headphones will give you a much better soundstage to judge your mix by and it also help to reduce any bass build up.
3. I would say it is very important, if the bass section is your major concern. When mixing if your headphones are tuned to have more bass then it will be difficult to translate that from your headphones to monitors, stereo speakers, car speakers... You want your phones and monitors to be as linear as possible.
4. I hear you but sometimes it can't be avoided. I learned to mix to my ear taste. If it sounds good then it is good. Trust your ears, that's what the lay person does. Furthermore, if you are clipping your speakers it sounds more like you need a limiter in your editing software somewhere to keep you mix below the clip threshold. Remember the loudness wars are over its all about dynamics, thank god!!!! I would rather turn up a volume knob and have dynamics than the music sounding as loud as possible regardless of where the knob is.....
5. I guess another question would be what are your thoughts on used headphones, it seems kinda gross to me but besides that factor would there be a risk of quality loss due to usage over a period of time?
5. It isn't a completely bad thing... as long as they weren't abused, which unless you know the person you wouldn't know. Ear pads can be changed that isn't a big deal. But you certainly don't want a driver on its last legs and then start pumping Gobs of bass through them.. then kaboomm... you need new anyway.... but on the other hand having a decently used pair of broken in headphones isn't a bad thing either. If I were to buy used it would be for casual listen, I would buy new for mixing..
The unfortunate thing about headphones is the perfect headphone doesn't exist. If it did there would be no headfi no need for choice. They all have their strengths and weaknesses. Then add to that everyone hears differently. It all comes down to a compromise. So to come to an answer of which headphone to get..... try to avoid paralysis by analysis.... don't over think it.. ask questions( your doing that), do some research( your doing that) then you will arrive at your answer.
Then once you purchase your headphones learn their traits, understand their strengths and weakness, listen to your mixes on various speakers (mixing montiors, home speakers, car speakers and portables). This will give you a really good idea how things translate.
So if your budget is what it is... you will have a dedicated mixing room(close the door), I would go with the beyer DT880, it is more linear than both your choices. The DT880 has a proven track record and it is the best compromise between everything.....
Hope this all helps.... Headphones are so subjective.. so many variable to take into consideration.
Peace OOK
THANKS AGAIN ! 
