i think its not really a matter of f2.8 or what..
maybe you can see what focal length you want?
if you just concern about aperture.. i would suggest you take a look at f1.8 instead? 50mm f1.8 is the most value for money lens to begin with. LOL
plus you've posted many posts without being sure on exactly which lens you want, or at least a couple of lenses. maybe you should go and research first before posting so many threads!