@tlotz: Thanks for your reply. It gave me some confidence to do some more testing. So after many flashes and system resets here are some of my results.
1st transfer test: CodeGuys DS1E firmware DVD9@12x max....I'm not sure what happed here??? I couldn't bear to let it finish--it hurt my ears too much.
2nd transfer test: Same Disc back to Dell DD06 firmware
3rd transfer test: Same Disc Official DS1E (via DS1C flashfix'ed followed by official DS1E)
4th transfer test: Same Disc CodeGuys DS1E firmware DVD9 @10x max
So I think it is safe to conclude that the JLMS XJ-HD166 (no "S") with Dell firmware DD05 or DD06 is an OEM HD166S (not a big surprise I guess, given the name )
It seems that my problem with the first transfer test was possibly caused by not going to official DS1E before flashing with the CodeGuys Firmware? Either that or I had two bad flashes in a row before going to the official firmware.