It's usualy a driver related problem /not allways but usualy/. And if it happens when you try to play online games i suppose your firewall may be unable to keep up with the traffic, and because it's suposed to filter all network traffic to secure it it is blacking out.
So... check your firewall. Report what firewall do you use. Switch it off temporarily for test purposes /and better switch off the resident driver from the network settings/ and see what happens.
I assumed this "Killer Xeno Pro Gigabit High Speed Online Gaming PCI Network Interface Card" is a discrete network card.
Then you should go to BIOS and switch off ACPI and test it that way. And also another question - did you try to load your system with something graphics intensive but offline - like a SP mode game?
Or better run a furmark test - just to render out problems with graphics system /and pretty much with other hardware like memory too/.
OK, after all - are you using your onboard network or this EVGA Killer Kseno whatever network card, which is a discrete card, or both of them and is it crashing with both?
ACPI is switched in the BIOS - don't you have a user manual for our mobo? You may download it from your mobo manufacturer's site.
Also check the site for new network drivers and possibly for new BIOS.
Not bad idea is to check for new drivers for this EVGA network card too.
If your computer is working well with just one of your RAM sticks but not with all of them, then your problem is most likely in memory. Run memtest86 to see where exactly in your RAM is the problem. It pretty well may mimic an IRQ error. And it's most likely just one of your 4 modules, just need to figure which one.
Also /as chosenlast mentioned/ you may check your crash dump.
What ram do you have because if you have ram that is not rated at 1.5v or lower it will also cause this problem and/or eventually fry your memory controller on your mobo. This is the case with all of the new Sandy Bridge platform chipsets. Just a thought