hey guys i have i5-4670k and what is the average ghz i can overclock to? have aftermarket fans( noctua d14) 4.5ghz?

and what motherboard should i get? still deciding... Gigabyte sniper m5 mATX or udh4/udh3 or any others u guys can recommend? im new to oc-ing. and dont plan to overclock my motherboard as i dont think i need it. just going to clock cpu and gpu.. :-) btw clock motherboard got wad advantages? thx guys