I can't say much about that.. Even in my own country prices vary so much, that it's hard to compare sometimes.. So no idea about yours..
I usually shop around, compare prices when I want to make a purchase, since it changes a lot of course, I just check websites and folders from the local pc stores.
I'd say make sure your processor is a good step forward, RAM and graphics card too... as big a step as possible, within your budget.
Try to avoid certain 'packages' that they sometimes offer, at least over here it is better to pick and choose the right components and have the pc store assemble that for you. And if your old pc still has good Hard drives and you can transplant them, you don't need to spend money on that yet, perhaps, leaving more money for the more crucial components..