Should I get an antec 300 or another mid tower/full tower case?

I would wait for the sales in the next ten days in the usa. The antec 300 has been as low as $40 shipped recently. If you need usb 3.0 on the front connector, a few inexpensive units are starting to use them, but your board also needs a usb 3.0 pin connection; not many boards have it.