The new Bulldozer chips aren't really good for gaming, can be actually slower for gaming than the previous Phenoms. But since you want to do all the other stuff, they're certainly something to consider. They do very well in heavily threaded applications. Can't say for certain since I don't use these apps, but I bet the rendering and modeling stuff can profit from it.
But since you're working on a budget, I'd try to just get the fastest CPU you can afford, regardless of what architecture it is based on. New architectures are generally a step forward, but the older stuff still "gets the job done" as you say.
For graphics, can't really say. Not at home, kinda tricky to go delving through comparisons and reviews right now. But for Nvidia my recommendations start at GTX560 (or 460, but it's kinda obsolete with the 560). Those cards come in at 200-250, so I'd say stick with what you have now and see how that turns out. If it's not to your liking, you could always save up some more and upgrade GPU later, at least then you're sure it will be a good improvement.
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