Every time I have installed Sabayon (3.3 and 3.4) on a Dell laptop, X11 will not work after install. At all.
Instead of trying to figure out the right settings for X11, I have found out that booting knoppix and just copying over the xorg.conf file to your sabayon installation (you have to mount the partition read-write) works perfectly. I hope this helps out someone.
Note 1: If knoppix can't figure out the file system of partition hd(c on a inspiron 1100)2, just dump the file on the boot partition, and copy it over in sabayon.
Note 2: Test the new config file by using "startx". If it gives you 2 terminals (no kde), it works - just reboot to get the login screen.