burn speed?

I use a powerbook G4, with superdrive bought late 2002 (matushi or whatever makes the dvd drive- can't remember the spelling)...and I use a G5 1.8 at work (SONY DVD RW DW-U10A drive).

Question is, I've just bought some blank sony dvd's which say from 1x to 16x on them, that's fine, but in my settings in iTunes, do I set it to maximum possible or to 1x or 2x to be safe for the hardware's sake? Or does maximum possible just mean max poss that the hardware will allow? I've read through the apple link that is sometimes posted here re: updating the firmware for a drive if needed, I don't think I need to, but didn't know what I should set my burn setting to in itunes, and why is iTunes where we set this?

Thanks much
KB