Anyone know what the best settings for gaming is with headphones?  I have Sennheiser HD660S headphones but any settings I use have limited benefit.  I would love to use the 7.1 surround sound but when I do the voices in game from NPCs are very very weak and can barely hear.  I've had to down grade it to 2 channel just to get decent audio.   How do I max this thing out for great surround sound but also great NPC voice volume?

Where are you setting the option for 7.1 surround? In-game?
The Sennheiser HD660S headphones are not surround headphones. That means you can only use virtual surround with them. There are a number of virtual surround options available, but the best/quickest is the one built-in to the Nu Audio software. On the software's main page, you'll see the surround option towards the bottom in the section named 'Audio Effect'. Just click on the circle there to enable. In your game, you'll want to set it to 'headphones' or two channel audio (in combination with the Nu Audio software setting I mentioned) for the best effect.

Virtual surround is consistently terrible, as you noted.  Don't do that. ;)  The positional stereo that the game developers spend a lot of time and money creating is WAY BETTER than any 3rd-party virtual surround run-amok. Virtual surround is out-of-engine and is an interpreted guess, by people who didn't make the game, of where the sounds may be coming from.  That interpretation/guess is so, so, so often wrong.  Imagine it this way: close your eyes, listen to the game, and then repeat the sounds to someone else and tell them where the sounds are coming from.  That is effectively what virtual surround is doing.  It is operating in the blind and altering the positional information of the audio for who knows what reason.  It's crazy.  The stereo that the game developers incorporate into the game is in-engine and is based on a knowledge of where the sounds are known to be; it is consistently more accurate and consistently better.
If the game doesn't support surround, just use stereo.  Every time.  Never use virtual surround.
Edit: Your headphones are stereo headphones.  Use stereo.  Virtual surround is garbage.

As you've likely figured out by now, virtual surround effectiveness is quite subjective. You have various options at your disposal (Nu Audio, Windows, in-game). Try them all out and go with what YOU like best. 🙂 Just don't use more than one at once.