Since the Core i5-3570K is one of the fastest quad-core processors that you can buy, it should be more than adequate for your new build (in this thread
It's a matter of balancing where your budget goes. If you've got enough to get both the Core i5-3570K and the Radeon HD7950 along with an SSD and the other components in a fast gaming PC, you aren't having to make many compromises.
The relative importance of CPU clock speed and number of cores will vary depending on the games that you're playing.
i7-4770K, H70, Gryphon Z87, 16 GiB, HD7950, SSD, 2 HD, Blu-ray, SB ZX, TJ08-E, SS-660XP², 3007WFP+2001FP, RK-9000BR, MX518
i5-3570K, GeminII-S524, P8Z77-M Pro, 16 GiB, HD7770, SSD, 2 HD, Blu-ray, InifiniTV4, NSK2480, 55" TV; Asus UX32VD