A friend bought the cheaper black aluminum case from colorcase and was happy with it...case size won't matter too much, but if you go bigger, you'll have more room and need more fans to provide adequate cooling (assuming you're overclocking). If you're not overclocking, anything with a fan or two and a CPU cooler will be plenty fine. Personal preference and what you've gotta fit in there is more important. If you've only got one or two HDD's and one or two CD/DVD drives, a full tower is way overkill. If you're using water-cooling, running raid, have lots of PCI cards you'll be using (multiple nics, sound, video, DVI, RAID, whatever) you may want the larger case, or a better mid-tower with lots of fan mounts to keep those cards cool...I'll be going for the black Antec SX1040 for my setup (see the PC Spec post if you care =)
/L.A