While processor speed is important, I will take a slower quad-core over a faster dual-core any day of the week. And I will take more RAM and a slower quad over less RAM and a faster quad. And better graphics with a slower quad over lessor graphics and a faster quad.
And I will take more slower RAM over less faster RAM any day of the week too.
The "sweetspot" for RAM is generally considered 8Gb. When it comes to "the most bang for your money", less RAM and performance is noticeably degraded, more than 8Gb and any performance gains are marginal, if noticeable at all. Of course, with more than 4Gb, you need a 64-bit OS.
And finally, hard drives are for backups, songs and videos. I see no reason to bottleneck a new computer with a HD these days. Get a 250-256Gb SSD as your boot drive for the OS (and page file) and all your applications. You won't regret it.
And finally finally, don't try to shave costs by trimming the budget on your power supply. You don't buy a fancy new Porsche then fill it up at the corner Tobacco & Bait Shop. And you don't need gobs of power either. Most users, even with power hungry graphics cards, big quad-core CPUs and gobs of RAM, can do well with a quality 500W 80 PLUS "Gold" supply.