[Goku]

For overclocking, generally the improvement depends on whether the game is CPU (SC2) or GPU (Metro 2033) bound. 2500K is cheap on newegg at the moment. If you do not feel the 3570k is worth the premium get that instead. Overclocking can also allow a processor to last a lot longer. Take for example the Q6600 that was released over 5 years ago. Stock clocks were 2.4GHz on that quad core. At those settings it was great for its time, however the past few years it started to show its age. Back then and now people overclocked to 3.6GHz, thats a 50% boost in free performance. These people went to a far better gaming experience at a flick of a switch basically. Thats why I think overclocking is great, free performance especially for down the road.

Audio cards well that all comes down to what you think. I have been using a sound card for almost 5 years now. I notice the difference between onboard and a dedicated sound card all the time. You could always put off the sound card and wait for a sale. I see deals a couple times a month anyway.