Well Tumor its like this, the longer you wait to build, the prices will fall or more advanced processors, faster ram, etc will become available. It depends when you want to "deploy" your new system. I've been stuffing money into savings so I can buy and build it all at once, versus buying this component, that component, etc
Read tomshardware.com and
http://www.anandtech.com The benefits of dual cores are out there. Just because one application hasnt been coded to use it doesnt mean it wont in the future. I mean, I'd hate to buy an FX then a few months down the road, wish I had for the dual core performance gains.
Your money. Your choice. We're just providing the comments
Check those sites out, lots of good information.