Mastering woes - any advice welcome.

I'm trying to master on my own in LE 8 using the onboard tools. I think I'm doing a fairly "decent" job and I gage that by how the music sounds in my sound studio on wheels (my car), a pair of Bluetooth (over most of the ear) headphones, a better pair of wired over the ear head phones and a plain vanilla pair of Apple, 1st generation headphones.

Unfortunately, the plain vanilla pair of Apple, 1st generation headphones are the ones giving me the most problems. The problem is certain piano and acoustic guitar virtual instrument notes are so loud (or harsh) over these earphones, they almost burst your eardrums - especially when the volume is up high. I know the frequency response for cheap ear buds like these is probably pretty limited but since so many people use similar ear buds, I want to make sure I do the best job I can do with them.

What I've tried to correct the problem:

- I've gone into the EQ to cut the higher frequencies both in the music arrangement (on the instrument track) and in the mastering plug in.

- I've hunted for piano key strikes over value "51" for velocity - the typical harshness cut off point

- I've dropped the mids - slightly...

How I bounce:

- 24 bit wav files to 16 bit wav with dithering on.

Is there anything else I can do to tame these loud, harsh, piano and acoustic guitar, upper frequency notes other than going into each mix on a loud note witch hunt! Thanks.