There should be an option under AMD Overdrive called "Power Limit settings"
Increasing this above 0% will allow the GPU to draw as much power as it needs if it needs it beyond its limit. It does the opposite when you turn it below 0%. The R7 265 has a limit at 150w, but typically draws around 110w while gaming.
Lowering it by 20% will set the limit at 120w which probably wont change anything because the card doesn't typically use that much while gaming but will prevent it from going over it for whatever reason. You can lower it more if you like I think. My R9 290 goes as low as -50%
Word of warning though, don't use this panel for overclocking, it sucks and causes only issues.
If you're curious about your power supply and what it can handle, read this:
http://www.hardwaresecrets.com/article/Thermaltake-Purepower-430W-NP-Power-Supply-Review/332/1
This actually seems like a really bad idea waiting to happen, as your PSU has a single 12v rail @ 18 amps lol