Well just from going of what others are saying, there is probably no point starting mining now, considering the dedicated hardware that is coming out, and the reward dropping to 25btc. That said, others may have a different view.
This!^ However, if you were planning to build a gaming PC anyway, then why not make it dual purpose.
If you are mining with the 58xx card, you can absolutely use the on-board graphics for general computing, light gaming or watching youtube.