Hardware Compatibility

Hello, I bought my Alienware PC back in 2012 and haven't upgraded a single piece of hardware then. Now I wish to upgrade it, but I have some questions before I do so...

My PC uses a GT 545 for graphics, an Intel-Core i3-2120 processor, 5 gigs of ram, and an Alienware O8PG26 motherboard.

I'm thinking about getting a GTX 970 FTW GPU for gaming, but will it be compatible with my rig? I suppose I would need to change the motherboard, right?