Just finished building new computer, having problems

[CamNR]

i just finished building my new system, but i have had way too many issues along the way. specs are as follows: asus rampge IV extreme, intel core i7-3960x, asus nvidia gtx 690, 16 gigs g.skill (4x4gb), 1TB WD Black series in the Thermaltake Level 10 Gt case. So my first issue was that one of the dimm slots in my motherboard was screwed up so I am down to 12 gb ram which is fine by me, considering 12 gigs is more than enough to run any program or game I can think of, then when i received my graphics card, it wasn't working properly so i re-seated it a couple times and it started working, but now I notice my computer seems to be running slower and less reliable than it did when i first had it running with my gtx 260 (I didn't install the 260 drivers). I am averaging a higher fps with better graphics in most games with the 690 although today i bought 2 27" samsung syncmaster monitors along with a razer blackwidow ultimate keyboard and now whenever I play a game it freezes and I have to restart my computer within 10 minutes of starting the game up. Now I'm not sure if this is just added issues to my motherboard or if I have also received a bad graphics card or it may be a simple software problem, not sure. The last time I built a computer was 5 or 6 years ago so I am a little bit rusty so this very well may be a screw up on my part but I have not been able to find anything that is connected incorrectly or anything. Any input would be greatly appreciated.

 

[Deemo13]

What power supply are you running?

 

[CamNR]

rosewill bronze 1000w

 

[CamNR]

I could understand my system being unstable if I had been doing some overclocking or anything but I haven't done anything yet, everything is running at the standard clock speed and my cpu is running at its default turbo speed (3.9Ghz)

 

[CamNR]

the only thing that has changed in the last 2 days besides the monitors, is what is connecting them, before i was using dvi cables but my new monitors dont have dvi input only hdmi and analog so i have my primary monitor connected with an hdmi->dvi cable and secondary is with analog, is it possible that the hdmi cable is causing issues considering it isnt a new cable?