The thing is i already have the matx setup for a week now. I want to try out the mini itx board just for a change and return the matx setup right now and get the op setup. I still want to stay with 2500k because i dont think its that worth replacing since its not that of a bug difference between IB and SB. As for the gpu, i already have the 670 from gigabyte. Its not a reference cooler so it will blow the hot air inside the case.
in that case, should probably go with a silverstone SG07 or 08, both great cases with decent side exhaust. don't really have any hard benchmark results for motherboard performance on the P8Z77-I, Z77E-ITX vs standard ATX configurations but they'll be more than sufficient for building a tiny gaming system with. I've seen benchmarks coming from inferior ITX boards with great framerates in recent games/high detail settings.