will a 500w be enough to power a R7 265?

It is ALOT less powerful than the 265.

Also, it should clear just fine. The GPU PCB is always VERY close to the RAM slots on OEM boards. They would never design a board where it would not work though. I'm pretty confident that a longer card will have zero issues fitting.

http://i.imgur.com/m36e400.jpg See how it is here? just like yours. There is clearance. No problem.

http://www.tonymacx86.com/attachments/user-builds/76771d1387156434-dyuhas-dual-boot-bitfenix-phenom-m-matx-build-i7-4770k-ga-z87mx-d3h-16gb-2400mhz-memory-gtx-770-4gb-img_0486.jpg here is a great example. It is perfectly normal to have the RAM almost touch the GPU on an mATX board.
 


ill see what happens thanks for the help the ram slots are slightly below the gfx slot so it might just work

EDIT: this gtx 750 ti will fit most likely and its in my budget range http://www.microcenter.com/product/429764/02G-P4-3753-KR_NVIDIA_GeForce_GTX_750_Ti_Superclocked_2GB_GDDR5_PCIex16_29_Video_Card