SLI/CrossFire is when you connect two video cards in order to increase performance. SLI is for nVidia and CrossFire is for AMD
Hope this helps
Wow really nice build thank you! Although is $300 for a video card really that important?
Also what is the "2GB" on the Graphics card....what does that mean?
Sorry >.<" im a complete dummy at computers
The 2gb refers to video memory (VRAM) which is RAM for your graphics card... You need more RAM for multiple displays but 2gb (you might even get away with 1gb) is fine for your needs
Thank you so much! You've been a big help!
Also 1 last question if you're not busy:
Do i need to purchase any other components like a Sound Card/USB ports? or anything at all? (Besides the monitor/OS/mouse-keyboard)
I'm completely new to building a computer as you can see x.X;
Sound cards and usb hubs are usually unnecessary unless you have a specific need for them (i.e. you know that you will need more front panel USB ports than your case offers or you know you will be using high end speakers and can benefit from better a sound card).
If you have any other questions I'm all ears (I know how confusing a first build can be but it will be worth it once your done )