Requirements:
Qoob Pro & SX Modchips
Everything You Need To Install These (link)
One Female 25pin Connector
Two Male 25pin Connectors
Wire Cutters and/or Dremmel
Extra Wire (30 guage)
Super Glue or Alternative
Eletrical Tape
The first thing you want to do is use your 30 guage wire and solder it onto all of the points outlined in the diagram above. With the Cube motherboard facing you run the wire to the right hand side and make sure there is enough to reach the surface you are using to hold your Cube into place.
Next prepare the 25pin female connector by filling the leads you are going to use outlined in the diagram above with solder and then proceed to solder the wires coming from the motherboard in their appropiate locations.
Now take both of the wire adapters that come with the Pro and SX chip and cut all of the wires from them leaving only 1/4 of the wires left. Take both of the switch plugs from either of the sets of wires and plug them into their appropiate locations and then wire them to the 25pin female adapter as specified in the diagram.
Following that you're going to want to fill the 25pin male adapaters leads with solder then solder on both adapters for the Pro and SX. Notice you'll be using opposite sides to solder onto. Make sure to get the power wires right as you don't want to blow your SX chip by plugging it into a 5V powersource. Now test your Cube using the Pro chip. Note at this point in time you must leave the case off for testing purposes. If the Pro chip works then test the SX. Please make sure to double check that the SX is using the 3.3V powersource!
If either of the chips do not work make sure you are plugging them into the connector as tight as possible and if that doesn't fix the problem please double check your soldering job. Make sure there are no crossed BIOS legs and/or crossed 25pin leads as this will result in the Cube not booting. Once the Cube is booting both chips you can move on to the next step.
Now if you're going mount the female connector where I did simply cut out some of the air intake grill using your wire cutters or you can use the dremmel to mount the connector elsewhere. Unhook the reset button assembly connectors for the next part. Put the case on half way and leave the back off of the Cube for now. While holding the case half way down gently slide the 25 pin female connector through the hole you have created for it and then let the case slide down. Now reach through the back and connect the reset assembly connectors then lift the back of the case up some and attach the back panel you left off.
To secure the 25pin female connector glue it down into place.
Finally you may wish to wrap your chips with the eletrical tape to make sure they don't get zapped with random static eletricity. Now you can switch the chips at your leasure, but of course make sure the Cube is powered OFF before switching them!