A question for the Masses: Camera Glass v MP?

Ok so ive been basically appraising my gear recently. Ive been looking at all the things i 'need' to get for me to be happy. Basically ive been wanting to get the Canon 400D.

But then i wondered. what can a 400d do that my 300cant? Photoshop can interpolate really well, to a 10.1 MP image with too much dramas involved...

So i put it forward to you. If you had a 300D (6.3MP) camera with original 2 lenses, would you:

A) Replace the glass (nothing crazy expensive but good quality)

B) Upgrade the camera body to a 400D (6.3MP to 10.1MP)

C) Upgrade the camera body to the 400D with lens kit

I realize that there are probably a fair few different opinions in the matter.

What i really am trying to work out is what will be a better investment of money in regards to image quality.

*NOTE - This is assuming i have some form of skill with a camera and can take advantage of the pro's of each option... This had yet to be proven though =)

© Kirza

© Prawny

I look forward to your opinions and replies and value any input given.

Thanks again for reading.

Photo credits: Kirill Zdorov, Dawn Hudson.