good point, in terms of the aero-800, it heavily resembles a corsair 780t, its a big unwieldy case either way and aerocool doesn't have the same build quality reputation backing up phanteks. not to mention, when you go tempered glass, you never go back....
the realan steel E-C3 is smaller, MUCH smaller. as in, so small you only get one usb 2.0 port and no gpu small. If you plan on doing a serious build I do NOT recommend the E-C3, its outdated and ill equipped for a proper build.
if you are set on a 60 dollar price point for whatever reason, you aren't likely to see anything that tops the phanteks p300. I strongly recommend you take some time to research more options. if you are after longevity, try and go with the brands with the reputation behind them. they have it for a reason. Also take into account the parts you want to put in it as that will determine ultimately what you get. I hope this helps and good luck to your first build =)