a MKII? get a MKIII!
the best deal is to get two 16gb sandisk extreme cards, only 99 a piece now and if you shoot a lot you can be downloading one and keep shooting with the other.
Just bought a Lexar 1000x 16GB CF for my 1D4 and soon to come 1DX. It is UDMA7 and it is 2 times faster than my Sandisk Extreme Pro 16GB.
1GB of photos using a Firewire 800 Sandisk CF Reader take 1 minute with Sandisk, and 28 Seconds with Lexar.
Previewing and zooming are a lot faster in camera and I can take almost twice as many photos in high speed than i used to.