I'm going to say that you could possibly modify your existing fans. The link that you posted to ebay is the fan with the 7pin connector.
Here's the pinout of the 7 pin fan female connector that mates to the 7 pin male connector on the pic18
I
think that the pinout (left to right) is ...
pin 1 red +12v psu#2
pin 2 black GND psu #2
pin 3 black GND psu #1
pin 4 red +12v psu#1
pin 5 yellow sense (RPM)
pin 6 blue control (PWM)
pin 7 n/c
I know for sure that pin 1 and pin 4 are commoned about 2" from the fan, as are pins 2 and pin 3. I think that this way the fans have the ability to get a redundant feed from both power supplies.
Your 5 pin fan looks to be ...
pin 1 black
pin 2 red
pin 3 green
pin 4 blue
pin 5 n/c
If you overlay both connectors from the n/c pin I'm pretty sure the pinout / color coding is the same (green is typically the other color used on 4 pin PWM fans to denote the sense line)
By design ( and for very good reasons ) the connectors are keyed, and there's no way for your 5 pin female fan connector to physically fit the 7 pin male connector on the controller. In order to get your 5 pin cable to fit you would either have to (1) build a mating cable or (2) physically remove one of the keys (the one near the black cable) with an exacto knife or similar.
Once you have removed a key you have compromised the inherent safety and design of the connectors, so I cannot in good faith recommend that you try this.
I have no idea how the pic16 and pic18 controller boards are wired, and there is the possibility that if your C6100 has a single power supply the power/ground for the single power supply gets routed to pins 1 and 2 of the 7 pin connector, in which case removing the key would not work as you would need to have ground/power on pins 3 and 4.
The safe route is to purchase the 7 pin fans.
However, I'm going to go on to say that the stock fans are too loud for my preference, and I've replaced the std fans with Evercool fans (as recommended by PigLover in the "Taming the C6100" thread). There are others that have recommended different fans, and I'm about to experiment with various San Ace fans. I have not yet found a source for the 7 pin female connector so that I can build my own custom cables.
The closest that I've found is a 6 pin pre wired connector
here on ebay . I've purchased these (color coding per pin location is wrong but that's an easy fix) and I'm about to experiment, and I'll leave it to your imagination as to how I'm going to get a 6 pin female fan connector to mate with a 7 pin male connector on the fan controller.