Right now I own an Olympus Stylus SW 8010 and get average quality 4x6 prints and very grainy 8x10 prints. I am looking to buy a Pentax Kx SLR (which is 12.5mp) and I was wondering if I will get better looking prints? I print out every image as a 4x6 and select a few good ones to get blown up into 5x7 or 8x10 so I would like to have very clear images.

Also, I've heard that anything over an 8mp results in clear 5x7 and 8x10 images but grainy 4x6's...is that true?