You already have the 300D. Dump money into lenses, don't worry about upgrading the body unless you absolutely require. The 300D's image quality is quite awesome, some people say it's even better than the 20D/350XT. Why? Same size, less pixel density (6MP vs 8MP). And less noise in the lower ISOs (quite negliable) such as 100, 200.
If you're shooting food, you'll have quite a bit of light control. You could easily shoot at ISO100. I'd keep your body, and save up for glass. 35/1.4 and the 50/1.4 are both awesome lenses. It just depends on how big or small the food you're shooting
Also what kinda perspective... search for 35mm and 50mm shots.