No point in using higher level then the music you listen or the audio in the games you play have. I have 32 bit precision, its ok in all the games I have tried. Higher is good for low volume listening. What was wrong for you?
Nahimic is not very good software. As for the EQ, try using it in the reverse mode. So lower the freq you don't need instead or rising the freq you need and then rise the system volume. If you reach more then 100% system volume with EQ, the clipping will appear. Also, EQ is disabled at 100% volume too.
As for sampling rate, the only issue I have is the spatial sound in Windows hard locked to 48 KHz 16 bit or something like it. It always switches to this setting. Really spoils my life since this feature is much better then any virtual 7.1. Also, if you listed to music through ASIO, the bugged drivers won't switch the sampling rate back afterwards. This results to missing sound in the system. So if you listed to 44.1 KHz, then set driver to 44.1 KHz.