You don't need
the Z77 to get a decent overclock on a 3570k.
I just did a bunch of Google searches of people overclocking 3570k's with the Asrock z75 motherboard and it seems that as long as you have adequate cooling and a decent chip, you should be able to get your 3570k running stable at 4.5GHz.
Here is an example of someone with the 3570k overclocked to 4.5GHz with the Asrock Z75 Pro3 motherboard.4.5GHz CPU-Z Validation
4.3GHZ CPU-Z Validation
Check the vcore's on those validations too. That all depends on how well your chip clocks though so don't expect for the exact same vcore to work for you. But who knows maybe your 3570k will be really good clocker and need less voltage.
So if you will only ever use one GPU and don't plan to push your overclock extremely high then the Asrock Z75 Pro3 will work. If you will be happy with 4.2-4.5GHz overclock and only ever 1 GPU then the Asrock Z75 Pro3 would work.
EDIT: Just saw you aren't dead set on just Asrock. I use Gigabyte motherboards a lot and they work great and overclock decently. I run my 3570k at 4.5GHz 24/7 with 1.176v vcore with a Gigabyte Z68X-UD3H-B3. I also have a Gigabyte Z77X-UD3H and it will run a 3570k at 4.5GHz as well(haven't had the time to try pushing further than 4.5GHz on either motherboard yet).Edited by Dark Volker - 7/12/14 at 6:23pm