Below is your quote and I put my responses after each of your questions starting with the indented "Reply".
1. I was recommended headphones with a mic attachment, instead of an actual headset, because the sound quality is much better. If I told you I was going to use the headphones/headset for BOTH gaming and music, what would you say about that statement?
Higher sound quality VS the virtual sorround gaming headsets can provide.
Reply: I have been on a quest the past couple of months to find a great set of audiophile headphones for gaming also. This was because my Tritton AX PRO mic started going out and after using them for a few years, I realized how unsatisfied I was with the audio quality of them as well as most gaming headsets out there. I had tried all the big Gaming headsets out there: Astro A40/A50, Turtle Beach XP Seven...ect. All of them had something I was dissatisfied with and I had two defective Astro's which lead me away from that brand (I guess it was just bad luck). One gaming headset that I actually like is the new model Sony Pulse for $150 (it has both 3.5mm plug-in and usb wireless audio options)
2. If I told you I was to spend 100-150 US dollars on the headset/headphones, do some headphones pop into mind? Or perhaps if you have any personal experience with a headset in this price range?
Reply: I have tried a few headphones (not headsets) recently, including :
-Ultrasone Pro 900
So, The only ones that are in your price range (or cheaper) are the AD700 and the HD668b. To clarify, I actually kept the HD668b because the audio quality was amazing for a headphone only costing $50. It rivaled the other headphones close enough to where I could not justify the price difference compared to the Q701. Keep in mind the build quality and comfort was not as good in comparison to the others, but the audio quality was good enough to rival them. They had less bass than the DT990 pro, but more bass than the Q701. (Search the forums about the HD668b to get more info if you interested in them.
The Audio Technica ATH-AD700 are also in your price range of $100. They have an amazing sound stage on them, great for gaming. In many reviews of headphones...a reviewer commonly uses the AD700 as the standard to compare how wide a sound stage is. The only downfall to them is they do not have much bass. The bass is punchy and present, but it suffers with lower drawn out frequencies. A very good option though. I loved them for FPS games. They will shine with many genres of music that do not rely on a lot of bass (obviously).
Those are the headphones I have used and tested in your price range, and I ended up keeping the Bargain buy ($50) Superlux.
I also have the Ultrasone Pro 900 currently and really like them also, but they are about $300.
3. If i get a wireless headset, will the wireless feature decrease the sound performance?
Reply: Wireless headphones are pretty good now a days in my experience. However, their are a few draw backs that keep me away form them.
1) Volume levels - the wireless headphones I have used have been somewhat soft in volume. For example with the Sony Pulse, listening to them wireless, I have to have the volume all the way up and I still wish they were a little louder sometimes.
2) Battery life - The louder you listen to them, the less the battery lasts. Plus I always worry about the battery getting worse overtime.
4. I want you to take into consideration that I listen to a very wide variety of music, thus a set of 'forgiving' headphones, is one of my preferences.
Reply: I find the HD668b to do well with many genres of music. If you find them comfortable enough and treat them nicely, they may fit your bill and you save some money.
I hope this helps a little and gives you a place to start. I am no audiophile (yet), but I have definitely been obsessed with headphone the past few months and have done way to much research. There are many options out there (as you know) and it can be frustrating trying to find the ones that best fit you.