Rebates end on aug 15th....And if it goes up to its original price then find something with more ratings though antec is generally a good buy.
I dont think a full tower is totally necessary as long as you have good air flow. Full tower is roomier. I have the nzxt phantom and its huge and has plenty of places to route cables, and can fit nearly any card without worrying if hdd are in the way, but it is significally more than the antec 300. But then again after rebates on the above psu's you could possibly switch cases and i think it might be like 10 dollar difference after rebate...But like i said, the phantoms are big and I had to pull my desk out and have it angled to be able to fit into my space.