So after scaling an image down to the 640 x 800 pixel size the pic takes a huge hit in quality. Does this mean I should be using the vector format? I've been submitting jpegs and it just became apparent to me that may be a bad idea. I'm using Gimp for my art although I could convert to vector through inkscape. However, inkscape makes me want to strangle the first unfortunate person to cross my path. Am I missing something? Is vector the only way to go?
Vector isn't the only way to go, you can by all means make something 300 high res enough for a t-shirt print it photoshop alone.