more power?

so a holley carb and increase to a higher cfm? by increasing to a higher cfm wont i lose throttle response? the main reason i decided to go with the 600 is cause i was told id have better throttle response and that this engine aint set up to run past 6 thousand rpm anyways, it makes its max torque at 4000 rpm and max horse power at 4750 rpm, and on the wot torque/horse power graphs i have seen for this engine show a decline at 5000 rpm.
So based on that is why i decided to get the 600cfm, figured since it stops making power at 5000 rpm might as well run a 600cfm and have better throttle response. is there any kind of upgrade i can do to the valves or valve springs, ignition? i have a crane cams ls1 fireball ignition coil, but i do not have the box.