Live rock requirements for a new tank

[tHeHEYzeus]

I'm new to the world of marine aquariums and am putting together a 45 gallon show tank with a 20 gallon sump. I'm currently purchasing rock and realizing that it is pretty expensive. I was wondering how much regular rock I could get away with using combined with live rock to begin cycling my tank. I've already purchased 30 pounds of really porous non live rock which I'm pretty excited about.

I'm also planning on putting most of my live rock in as smaller pieces the middle compartment of my sump. This way it will filter all the water through the live rock.

Any suggestions would be much appreciated!

- Ryan