I'm looking to upgrade my PC. Overall, I'm happy with it's performance, but I've been getting a lot of micro-stuttering in games. I currently have an i7-930 OC'd to 4.02ghz, and 2 HD 5770's in crossfire. From what I've been reading in the articles on the site, it seems I should upgrade to a single HD 7970 first to see the biggest improvement. Also, from what I've been reading, going to a i7-3770k really wouldn't be that much of an improvement at all.
you don't have to upgrade your proc since thats more or less on equal footing vs an IVB i5, the 7970 would be a major step up for you and will definitely eliminate stutters in games with the recently released catalyst beta drivers.
Most definitely your graphics card. I am running an i7 920 @ 4GHz and it runs everything I throw at it just fine. I've always kept my graphics card up to date and my base system only when absolutely necessary. I am running a GTX680 OCed somewhat and it runs everything I throw at it. There are only a few titles I have to tone the settings down for. An AMD 7970 would suit you just fine. Or you can go for a GTX670 or 680 if you are batting for the Green Team.