You can widen your search to one HDMI and one DVI (which is quite common to find). An HDMI->DVI adapter is around $4 and the only thing you will lose from this is audio (which I assume you are not playing via a monitor anyway). Check the resolution on the card though, as the number of pins on the DVI connection indicates its maximum resolution achievable.

Thanks Michael.
 
I was looking at this one last night:
 
http://www.amazon.co.uk/gp/product/B00L4B7W0U/ref=s9_simh_gw_p147_d0_i1?pf_rd_m=A3P5ROKL5A1OLE&pf_rd_s=center-2&pf_rd_r=1YT2BDJ48CVQDZ8G79N5&pf_rd_t=101&pf_rd_p=455344027&pf_rd_i=468294
 
i thought I'd go for an Asus seeing as the Mobo is also Asus

I did the same thing when I built this machine for the same reason. That card has "DVI Max Resolution : 2560x1600" so will fit the bill for you. The actual height of that is probably 2 slots on the MB (due to the heat sink) and I would recommend installing it on one of the lower PCIe slots to keep the sink furthest from the CPU (the middle PCIe slot would probably make the most sense, as the bottom one may be too close to the bottom edge of the MB (pg 20 of this manual, the "PCIEX 16_2" slot)).
 
Especially in cold dry air, be sure to ground yourself to the computer case before touching any components, and do not handle anything by the "pin edge" as extra precaution. ESD (electro-static discharge) can do nasty things to circuit boards if not careful. The lever prong on the end of the PCIe slot will unseat the old card when depressed and should snap into place when the new one is fully seated.

Thanks Michael for your advice and for researching the card itself.
 
I've got an earth strap here somewhere from when i was building our non-Daw desktop, so I'll be sure to use it!!

Problem solved.
 
i ended up buying 2 new monitors with VGA inputs so I can carry on using my existing card