Need help quick: What image size for post processing?

[DxHatchback]

if im taking images to "the camera shop" aka ritz camera to have them printed from my digital camera, what image size should i take them after i enhance them in photoshop?

3200 x 2000

or

800 x 600?

i want the best quality possible

[PacAce]

3200 x 2000 would definitely be a lot better than 800 x 600 but what I do is crop and resize for the print size I want at 300 DPI. So, for a 6x4 print, i'll resize the image to 1800 x 1200.