Luc,
665- not quite so evil.... ( T-Shirt I once saw)
Blame distortion- early in my formative years I read Eddie Van Halen once say "you can't play a maj 7th with distortion all the harmonics start clashing and going all over the place" so I guess the 6th same thing. .
so Luc, brave on- play that 6th, wait better yet play that major 6/9 with pride. the sixth has a very soothing quality and even Brian Setzer used it to good advantage.
hit it up with some chorus and some delay, no mountains, just peppered enough, and play to your heart and soothed minds content.
here's one of my favorite tunes with a whole lotta 6ths.....brgnnn... whole lotta 6ths.... brgnnnn
"I Am Yours" - by Derek and the Dominos ( Eric Clapton's pseudonym band testing to see if the public loved him for his true creativity vs. his "Clapton is god" status at the time- nice work if you can get it!
[youtube]http://www.youtube.com/watch?v=AOiDF-BkeIo[/youtube]
hope it helps,
Dave B