Pc Turns off when I play games on Max settings

Since you have an overclocked edition gpu and your system is shutting off, I would see if scaling it back about 10% would help. See a post of another thread that I helped resolve:

"Anyhow, to underclock your gpu it will be like you were to try to overclock but instead we will ONLY shift the core clock slider to the left (slightly, the arrow is way longer than I want you to shift it but I made it that way to be clear what I was drawing):

So, to underclock let's try first just decreasing the core clock in 10Mhz intervals from 1160Mhz down to 1100Mhz at the lowest. I believe your default core clock is 1160MHz for the Powercolor 260x OC 2GB:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814131514
If everything works fine at 1150Mhz then let's leave it there. If it's something in between like 1130 or whatever, then that's good to; I don't care the number as long as your issue goes away and we are stable. If you are having to go way below 1100Mhz or at that speed it's not helping, we've already underclocked about 5% at this point and you may have to just rma the card.

MSI Afterburner will work on any card. Please go here to download it:
http://event.msi.com/vga/afterburner/download.htm
Click on "Download MSI Afterburner" and extract all, double click the MSIAfterburnersetup231.exe program to install it and make sure to avoid any add ons you don't want (if any). Do not download the latest beta as you are the guinea pig with that version and I'd rather you have a fully tested version for stability reasons which we are trying to increase!

Here's a good video that covers what you need to do but remember, instead of overclocking we are just shifting the core clock down a little (say 10mhz or 1-5% maximum of a DECREASE) and that number depends on whatever your core clock default speed is. Sometimes a gpu needs this to be more stable. Leave all of the other settings (memory voltage etc.) alone! Hopefully this works for you!
http://www.youtube.com/watch?v=W36EAnHp4oA

Also, I like Trave's recommendation of setting your power settings to high performance. Just go to Control Panel/System and Security/Power Options and click "Show additional plans", Click "High Performance" and then click "Change Plan Settings and set the monitor to never dim, turn off or put the computer to sleep, then click "Change Advanced Power Settings" and go one by one and set everything to where it never shuts down and when you are done click "OK" and then click "Save changes". It's easy to put back a different or the default settings later if you don't like this setting but for now we want to eliminate as many variables as possible and this is a good one that sometimes helps but I don't think it's the likely solution just yet. I really still think underclocking your card should get us the stability we are looking for but this won't hurt and may even help even if just a little!"

Take what you want from that but it covers pretty much everything you need to know to try it. You can always put it back afterwards to the out of box settings but I know this can stabilize a system rather well. Also, the same applies to your system overclock. If your cpu overclock is not as stable as it can possibly be this can further increase instability. Good move on upgrading the power supply by the way!

most likely your processor is over heating use a temp program like core temp and monitor the max temp during the time you can play the game possibly alt tab ever 2 mins or so to see if its getting increasingly hot if so invest in a better cooler like a cooler master evo 212 or an arctic cooling freezer 7 pro are idle cheap choices. if this isnt the issue try updating you gfx card's drivers and reseating your ram not that I believe that is the problem but cant hurt to try.