What I want to know is why you're wasting money getting a dual core if all that you intend to do with the computer is browse websites, check e-mail, and use chatting programs or whatever.
It will also be used for scientific computation. "General purpose" is intended to mean most modern applications/developments over the next 10 years or so. With this in mind, I think it would be short-sighted to get a single processor, when the dual-cores are currently minimal in price.
Also, you will be throwing out even more money if you buy a quad-core (especially the Intel quad core.. it's not even a real quad core.
). Few programs utilize multiple cores--and you don't need multiple cores to run day-to-day programs like Firefox. Hell, I run Firefox with few hiccups on a 400MHz processor back from the 90s.
Sure, right now there wouldn't be much of a difference, but I could see most software being written for multiple processors in the near future. But I don't know for sure, so that's part of why I made this thread.
Also, right now at Dell, the difference between the quad-core and dual-core is about $50, so I would go with the quad core if I don't get the AMD.
Regarding AMD vs. Intel, the stories I've heard lately suggest that AMD is behind in performance and that Intel basically left them in the dust with the Core 2 Duo series.
As far as single vs. dual core goes, without a doubt go dual core. Sure you can surf the web on a single processor 400mhz machine but when you reach that webpage that sucks your whole machine comes to a screeching halt. I also like the fact that I can still have a responsive computer when stupid things like Adobe Acrobat decide they want to hang and hog a whole cpu. This one is a no brainer, anyone who suggests otherwise doesn't know what they're talking about.
Dual vs. Quad is interesting, but I think ultimately this comes up to personal choice and what they want right now. If $50 isn't going to break the bank on this build then you might as well go ahead and do it. Afterall having extra cpu cycles is better than spending $1000+ and not having enough. I think the market is also trending towards multiple cores so you'll be ahead of the curve here.
If you step back and look at what is likely to change in the next 3-4 years that will make you want a new computer, cpu really isn't one of them. It'll probably be up and coming things like bluray/hd-dvd.