I like to put a HPF on tracks especially distorted guitar and slide it up to about 8-12k and listen to just the high end to hear what's there and decide if its doing much for the overall mix. Then remove the HPF and use a LPF to kill the nasty fizzle.
Then there's room for the cymbals and makes clarity better without boosting everything in the top.
27" Imac 2.93 ghz I7 12GB ram OSX 10.6.5,
MacBookPro 2.4 ghz duo 4GB ram,
Mackie Onyx 1640I, Motu Ultralite Mk3,
LA610 Solo, Logic Pro 9.1.6 DAW