Do U mix tracks with lots of HiEq then fix in master?

well. All begins with source, mics, pres and converters. If they don't give you the brinliance, liveness, air that you are talking about, you can olny try to achieve something wich is more or less similar. Maybe try to gain highs in the master bus and start mixing. I think that less EQs you use, more natural sound you get. Oh, and try to gain highs in ultrasonic band just to get a little more highs over 10kHz. If you're using freeware, try MasterEQ from PSP. It works untill 30kHz. Regards, Marcin.

Wow, I'm usually rolling off everything after 10k!

A couple of decent tips 

ONE. make some sonic room for each instrument and check where it sounds best in the sonic range. Guitar string squeaks, for instance, can sound horrible and if the guitar is there for the rhythm or strumming maybe you do not want all those high tones. A good way to check for horrible tones is to use a parametric EQ and peak it then sweep through the sonic range on an instrument so that each part of your sweep is boosted in volume by a massive amount. You will be amazed at how this shows you the horrible tones. TWO. Get some of those guitar hero tracks and check the layered sounds. Some of them sound quite dreadful on their own but come to a good mix when combined. A good example is 'Garbage' mixes.