Thumbnails for the homepage

I’ve been trying: “Simple Post Thumbnails” with no success, my problem is that I will have landscape and portrait images and I need a thumbnail on the home page to conform to a set grid design, so if it is a landscape image it can not be any larger than 163px in width, or 123px in width, the exact opposit is true if it is a portrait image.

Are there any thumbnail plugins out there that would suit my purpose?