From ebuyer's forum: "Asus P5K-E : Identical to the P5K Deluxe but has one less LAN port and a smaller copper heat-pipe cooling system up top."
and this from Hexus forum:
"I think the Asus P5K-E is almost identical to the Asus P5K Deluxe. The P5K-E has a single Gigabyte LAN port, whereas the Deluxe has Dual LAN. The P5K-E also has a less elaborate heatpipe cooling system, but I don't think these differences would hinder the performance of a P5K-E board which should be very close to the Deluxe but £30 -£35 cheaper. As far as I know the BIOS options on both boards are the same.
(If you peel back the sticker on an ASUS P5K-E board, you will see Asus P5K Deluxe stencilled beneath it.)"