Portfolio Image Size

I need to decide what size I want my final portfolio images to be presented and printed off as. The smallest we can choose is 8 x 6 inch and maximum of A3 size. I want to use a size that will help really show off the photo so my initial thoughts are as 8 x 10 inch (approx A4). I will discuss with Steve on what he feels would be the best size for my images too. I feel that 8 x 6 would be slightly too small and am tempted to try A3 as the images are quite large in regards of file size and the Canon 500D (the camera I used at the start of the course) takes up to 15MP images and my new Canon 550D takes up to 18MP images so they images should stand up to being taken up to A3 however as some of the images will be cropped in photoshop this may show up if blowing the image up too much.