Yes, but it is a bit overkill for me. I wonder why they didn't make the CX600M with 2 cables as well.

I know, but I see no other option. Even if I use 2xMolex to 1xPCI-E adapter all the current is being drawn through one cable again, because there is only 1 Molex cable with CX600M.

You can use the 8pin 12V thats suppose to be for the CPU. Either cut it and use 3x12V & 3xGND or look for a adapter.

I bought 6 Antminers, so would rather buy PSUs that can be used without any modifications.
And because I will probably mine for 1-2 months and then sell them I need 6 PSUs and not 3 big ones.

Oh nice. So 3x 12V and 3x Ground are needed per board = 6x 12V and 6x Ground in total?

That means I can just remove the CPU connectorand attach 3x 12V and 3x ground to one of the boards, right?

CX600M is £53.54: http://www.amazon.co.uk/Corsair-Builder-Series-Modular-Certified/dp/B00ALYOTTI/ref=sr_1_1?s=computers&ie=UTF8&qid=1390423038&sr=1-1&keywords=CX600M

I can buy this extension cable and remove its connector, thus not damaging the PSU cable, right: http://www.ebay.co.uk/itm/StarTech-8-inch-ATX12V-4-pin-P4-CPU-Power-Extension-/290992276563?pt=UK_Computing_CablesConnectors_RL&hash=item43c07dc453

Thanks.  Now, are we talking fire hazard or poor performance?

The official standard only allows for 75W on a 6-Pin PCI cable. I don’t know why this value is so low (it’s not a free specification for some reason). More info here:
http://www.playtool.com/pages/psuconnectors/connectors.html#eps8

I found several different information as to the max Amp on one cable (7A for 18 AWG seems most common) so 252W per cable.

Unofficially it would be ok but it’s at your own risk! Just make sure you have plenty of airflow running over those cables.

I don’t know why there are only three cables included. We can send you another cable. Please send us your full address.