Let me just put this out there too, i own the antec 300 illusion. I also did months of research before i built my system, and here were my requirements in a case:
1. Reasonably priced (got mine on sale for 55 bucks).
2. Great stock cooling (best cooling in that price range, nothing comes close)
3. Good looks
4. No modifications needed
5. I never intended my case to be an SLI rig, this is reflected in my motherboard (no xfire or sli support to make build costs cheaper, also my power supply is a 520w antec unit with 2 6 pin pci-x connectors, not a proper PSU for SLI rig, also lowered my system costs).
You need to look at a lot of things when choosing a case, mainly if you want it to be a purpose built SLI or Xfire rig. I didnt blindly choose the 300 illusion cause it looks good (but it does as a plus), i choose it because it was priced very well, fit what i wanted to do with my PC, and had amazing cooling for its price point (i feel bad for people who buy the 912 by cooler master, 300 illusion is superior in every way).
I would bet 1,000 dollars if you put my components into your 800D it would not only run hotter, it would run a LOT hotter. To me this is unacceptable for the price difference. I run a 2500k at 4.2ghz on stock voltage and my CPU idles at 28-30c (cooler master 212+) max load temps in prime 95 is 58c. My GTX 465 (notoriously hot GPU) maxes in games at 70c (this is lower than even some low wattage cards like the 6870). This is truly unreal if you google "gtx 465 temperatures", you will see that 85-90c is not an uncommon occurence for these cards, as the gtx 465, 470, 480 were all massively power hungry and hot running cards. I attribute my low temps to my case, with its dual 120mm intakes, 120mm rear fan, and 140mm top exhaust.