The most recent desktop I built was a full sized case instead of mid sized(what almost every desktop you see is). And it is amazing, it was significantly easier to build because of all the extra space and made wire management so much better and it stays a lot cooler. It is much larger, heavier and a bit more expensive but if you have room for it and wont be moving your computer around I would highly recommend a full sized case.
Also, everyone might not agree but I prefer to get a really nice motherboard when building a new computer from scratch. It will allow you to keep it for much longer and replace parts one at a time as you need them instead of having to do a complete rebuild when a new part isn't compatible with the older/cheaper motherboard.