one if the corsair obsidian 550d, and other is an antec p280, i read reviews and stuff, both are really nice cases and i would be fine with either of them.
now the problem i had with the 690 2 adv i have right now is that i cant close the back when i route my 24pin connector to the back and connect it to my motherboard. which of these 2 cases has more space in the back? i dont really get what measurements do cause it seems irrelevant to me.
also should i replace my h70 with a h100?? i have an intel i7 2600k no overclock.
The Corsair Obsidian 550d is a full 2" wider than the Antec which should translate to more room behind the mobo for cable management. I do not know this for a fact since I have no first hand experience with either case but that would be my assumption.
No real need to replace the H70 if your temps are okay. Even with some overclocking, you should be fine. You could do a push/pull configuration on the H70 (if you haven't already) with quieter fans.