Yes, wait, your fast 1g PC is still plenty fast enough. Going up 600 mhz would not imporove your gaming all that much. If you save your money alittle further down the road you will get alot more peformance gain.
But, on the other had, getting a deal like mobo and 1.6g CPU used for $180 is a good deal, and I would probably upgrade because of the low price. Plus you can sell what your CPU an mobo and recoup some money back. The deal is too good to pass up for me.