Am I able to change my graphics card?

Ok so I have just ordered my computer, which will arrive in a few days, but I would like to change the graphics card to something more powerful when I recieve the PC.

My specs are:

Motherboard: UNKNOWN (that's the problem)
CPU: AMD Bulldozer FX-4100 -- Quad Core 3.6Hz -- Overclocked to 4.0GHz
GFX Card: ATI Radeon HD 6670 1GB
RAM: 8GB Crucial Ballistic 1333Mhz DDR3
Hard Drive: 320GB

I do not know the power supply's wattage, or the motherboard, as the seller did not specify these, and I haven't got the PC yet.

I would like to replace the graphics card to either a ASUS NVIDIA GTX550 TI PCI-E Graphics Card - 1GB

or...


SAPPHIRE AMD Radeon HD 7770 GHz Edition PCI-e 3.0 Graphics Card - 1 GB






Now I am very new to gaming on computers, I know how to replace the graphics card, but I do not know whether it will fit in the slots, or whether it is compatible for my power supply. Can anybody help me out by telling my what slots the motherboard needs to have and what the minimum power supply I need for those card is, so that I can change it if necessary. Thanks in advance.

Well if the system has a 6670 in it already then the motherboard has a PCI-E slot so either the 550Ti or 7770 you picked will be compatible. You need to find the model and wattage of the PSU first though, to make sure the new GPU is getting enough power.

Just curious but why did you decide to buy that system if you were intending to change the graphics card? The mobo and PSU may be of questionable quality so you would have been better off choosing and assembling your own components.