Apologies,
K means it is unlocked for overclocking (multiplier up to 57 for a maximum of around 5.7 Ghz- if the processor can handle it within voltage specs).
If you think you will be happy with it at stock clocks then go for it. Still a great chip. It is not going to bottlekneck you by any means with a medium level GPU.
Remind me, what GPU you are thinking of?
A board like this would be good:
http://www.newegg.com/Product/Product.aspx?Item=N82E16813128538
Don't listen to the reviews, ignorant people.
Also, if you want to give me your budget and have me look up parts for you I don't mind. I love picking out components. Honestly, the best part about a PC is building it. Mine looks pretty sweet, side panel window, red and black color scheme, red sleeved cables, carbon fiber vinyl on the PSU and radiator, custom fans, white led's for low level lighting, ahhhh lol. Can't wait for my next build! I am going to build a computer in a desk!
I might buy the desk from these guys and build it myself:
Alright, now we, mainly I am lol, are way off topic. PM me if you need anything else.