150 watt Driving Light cable size

[Rock Trol]

I am planning on upgrading the wire harness to my two 150 watt FyrLyt driving lights. 150 watts is roughly 12.5 amps so a total of 25 amps will be drawn over the system. When I installed the lights a couple of years ago I just connected them to the existing driving light harness which consisted of a 30 amp relay and 10 gauge (6mm auto wire). The recommended relay size is 40 amps so I have just bought a 60 amp relay from Jaycar (overkill). I also want to install a 40 amp maxi fuse to replace the 30 amp auto fuse.

The question I have to any autoelec genius's out there is would it be worth while upgrading the wiring to 8 AWG (86 amp) wire? Is this overkill and not worth the effort? Do I also need to upgrade the negative wire to the same gauge? The website below suggests that the current wire size is more than adequate. Maybe I should just upgrade the relay and fuse only?

http://www.nissanpatrol.com.au/forums/attachment.php?attachmentid=59867&stc=1

http://www.bulkwire.com/wireresistance.asp

[Rock Trol]

I got all motivated today and decided to do the whole driving light loom. Now I have 8 AWG wire for most of the way and the 60 amp relay. The lights where a lot brighter under the car port than they where before (Sunny day) . According to the calculator I am only getting 1.137% drop in voltage.

http://www.nissanpatrol.com.au/forums/attachment.php?attachmentid=59885&stc=1