If you want to Overclock you have to Stretch your budget. If you are buying a Intel i5 2500K you need to take graphical advantage of it so I suggest you to buy Z68 Chipset board.
I just brought Asus P8Z68-V for my Intel i5 2500K and I successfully OC it to 4.8 Ghz. There are Z68-M (Micro ATX) boards from Asus which rages between 8-9 K
@OP, I can provide u good deal on Biostar TZ68 A+, Not overclocking beauty but will sufficient for Turbo Boost. Also Z68 Platform. Actually the marketing guy from Biostar is good friend of mine so if I can help u anyway on Non Profit basis i would love to
Do consider suggestion by fellow members but Personally i will save 1.5k-2k on board & will spend it on getting nice cooler which is must even though u r Planning Turbo Boost(Most are confident with Stock HSF so the suggestion)
Anyways let us knw if we can further help u in anyway
Impressive yes, but sure there are obstacles as well, the processor needs a new motherboard as it comes on a new processor socket, LGA 2011. That means reinvesting in a new high-end motherboard probably costing 200~300 EUR, and then investing in a new Sandy-Bridge-E processor which is probably going to cost you a steep 900 EUR for the most high-end model (which we will use today).
^^ what's the price ?? last time I remember it was around ~13k which will be too steep considering Op's budget but as OP is not replying anymore we can't say for sure if he is willing to increase his budget or not