Re: will I need to upgrade my PSU w/ addition of TV Tuner card,HDD?
Maybe, 300w is a low amount however this PC hasn't got any power sucking devices in, like a graphics card or water cooler.
To be sure use this eXtreme Power Supply Calculator
Its a PSU calculator, itll tell you what wattage PSU you need.
Intel Core i5 2500K /-\ 32Gb 1600mhz RAM /-\ Asus P8Z68/GEN 3
2x 256Gb Crucial M4 /-\ Crossfire XFX HD Radeon 7950 Black DD
Sound blaster Z /-\ yourpcperfect.com /-\ Windows 7 Pro