i chose that motherboard as you seem to like asus boards although i'm unfamiliar with it some one else may be able to suggest a better one. Most don't recomend those amd processers the 4100 is alot worse then the phenom ii chips from what iunderstand and they out perform them.
Most people recomend intel boards as oposed to amd usually the i3 or i5 chips they cost a bit more but most benchmarks show they out perform the amd equivalents. so youcan consider those 2 as well if they are within your budget.
It depends on what kind of load you are gonna put on it. For gaming i don't think you would use all 4 unless you 2 box (have 2 games running at once). Most people never really put enough stress on the cpu to use all 4 i wouldn't believe. Most may listen to music and surf the web or mute their games and listen to other music while gaming. Although those who edit video and do alot of hard core graphics work and such probably scream for more cores lol. And i didn't see a problem with your choices although you did not mention whether you had an operating system or not. If you don't you may want to get windows 7 unless you have another os.
As for video you can always upgrade better later when you have the extra funds. You can check out http://www.tomshardware.com/forum/forum-33-208.html and ask for suggestions specifying your build and people there can recomend something i've never really messed with video cards alot. I'm still using my on board nvidia geforce 6100 built into my board lol.