Unless you really like the idea of nice keyboards, I would save the cash and get a cheap keyboard and mouse. I personally have an under $20 mouse and under $20 keyboard. They work fine, for all I do. (Surfing, Starcraft II single player or vs. AI, single player FPS)
Asus is a good name for mobos, so long as your mobo supports your CPU it's all good.
It may also be worth upgrading the power supply. Unlike other components, a bad PSU can take other components with it if it fails, so a PSU is a terrible thing to cheap out on. A first guess at quality is to look for an 80+ rating, (or 80+ Bronze, Silver or even Gold). I think 550W would be fine for your build. I have an i5 2500K and 6870 (next step up or maybe on level with the 550) and a 600W PSU with no issues.
ex (the PSU I have):
NCIX.com - Buy Corsair Gaming Series CMPSU-600G 600W ATX Power Supply Active PFC 140MM Fan *3 Year Wrty* - Corsair - CMPSU-600G - in Canada