This should help,
Change the -190px to -175px in the above code.
Then add margin: 0; to the end of the code directly above.
You've also missed out a semi-colon in the above.
The changes shown in bold make the logo slices line up in IE6/Firefox, though I also noticed you have an 84px gap that appears at the bottom of the page in IE6, which probably corresponds to something in #topperch or #top. (see attachment)