I agree with bmwcrazy. It looks like gaming is a major hobby for you, so it will be an investment for years to come. It looks like your old one has served you for many years.
It is hard to give advice when we don't know how much you are willing to spend on it.
Without that I can only say that there are options, like keeping some of your old hardware, and replace the motherboard, processor and memory first. Plus a cheap, but better graphics card to go along with it, because that caused it all. Change the rest and replace the graphics card with a better one when you are able to.
Remember that you cannot just slap a great graphics card into your old machine and aspect it to work great. Your old power supply may not be able to keep up with it. Also your current processor will be a bottleneck.
On many hardware sites you'll notice that they think a new graphics card can give new life to an older machine. It's usually true, but that too has its limits. The X2 4000+ is rather old and it will be such a bottleneck - even with such a great graphics card.
I was in a situation in which I had a Phenom II and upgrading the graphics card didn't do much anymore. The only option left was to bite the bullet and change the processor too, because I wasn't getting any value for my money otherwise. That caused me to upgrade most of my hardware. It caused a chain reaction.
Looking at it from this point of view, you would only be able to keep your hard disk, monitor, keyboard and mouse.
In short: You really won't need the budget for a high-end rig, but it helps when we know your budget and if you are willing to assemble the parts yourself. That's not as hard as it used to be, but some care is required.
Edit: Oops. Corrected some silly typos.
Modifié par AngryFrozenWater, 08 septembre 2013 - 11:07 .