Seems you are asking two separate questions here are the images not sharp? or is it the grain thats a problem.. Some great advice given here, but may well disappear when you get the XTI but even then sharpness is often more to do with lens quality, and noise with the sensor.. 

To get the best results you need to ensure you have the best camera settings for the given light conditions.. Usually the lower the ISO the better... Postworking images also depends on making sure you have the right camera profile for the software you use..

Danny O'Byrne  http://www.digitalartzone.co.uk/

"All the technique in the world doesn't compensate for the inability to notice" Eliott Erwitt