Will a need a more powerful power supply?

Solution
750ti doent need additional power, other than the 75w that pcie can provide.so that 350w will do the trick. with only a few extra dollars though you can buy this EVGA which will easily ran the setup, including any overclocking possiblity!
Did you already buy this computer? you have some parts you should change out... no reason to get that CPU if you are getting a GTX 750 Ti. Also that ram, you should get 2 sticks of ram to take advantage of dual channel. If you want to stay with AMD go with an FX-6300. You will have to also switch the motherboard to an AM3+ socket board.