How do I get Calibre to convert at a set resolution?

[GoldThreader]

I own a Sony PRS-T1 and I am trying to convert a CBR to Epub. I want all the images to be the exact resolution of the screen of my device. The problem is my device isn't listed for calibre. I have no idea what resolution my pics will come out upon conversion but I do not want the file to be any larger than necessary. I have calibre set to Sony for my device but I have no idea what resolution that may be at. I have read the help wiki and it looks like it is possible to have calibre convert things at the resolution I want, but I don't understand the technical jargen. How can I set Calibre to convert every image to the screen resolution I want? Step by step instructions would be greatly appreciated.
The resolution I need each image to be at is:
Height 800
Width 600

Also if this is possible to do is it also possible to have calibre save this setting to do this for every CBR conversion?

Thanks for all the help in advance.