I assume you are going to mine an altcoin as mining Bitcoin with a computer is outdated by years
![Wink](https://bitcointalk.org/Smileys/default/wink.gif)
This IS the "altcoin mining" forum.
8-P
To the OP - foutside of CPU-specific coins, the CPU has pretty much zero effect on mining speed - I've got one machine on Ethereum running triple R9 290 GPUs with a Sempron 145 (older SLOWish single-core) without issues.
Videocard - depends on what you are mining on. NVidia usually is competative on production per watt, but tends to cost more so production per $ is lower, there are a few exceptions though and this generalization gets changes to the specific details as mining software changed, mining coin values and difficulty changes, and newer cards show up.