So were talking close to $450 U.S. Yeah, thats going to be a squeeze.
If your a gamer, which I assume you are I would keep the Pentium 4 2.8Ghz Chip, that chip is still plenty powerful for anything out right now, even though AMD is the better choice for gaming, it allows you the spend the money where its needed.
What I would do, is buy a new motherboard, PCI-E, nothing special, just something that will get the job done, and something that supports that chip, which I assume is Socket T. That will cost you anywhere from $50 to $75 U.S, E42-E62. That leaves you plenty of money to get another 512MB Stick of PC3200 DDR, assuming thats what your running, costing $50 U.S, E42. That leaves you at least nearly $300 U.S. E246 for a graphics card. I would get the eVGA 6800, great card at a great price. Much better than the Radeon 9600 you mentioned above, it wouldn't even compare. After the Video card, there is still plenty of money left over to buy a nice PSU, and a decent case, and maybe a couple of those nice accessories you have always wanted but never really needed. Like a decent keyboard Lol. You guys know what im talking about, people who are still using keyboards like this:
and thats exactly what they should be used for.
In any event, if you feel your lacking in processor speed in the future, you can easily upgrade with that newer board, to a faster pentium chip, or you could decide to scrap both the board and the chip and move to AMD. Either way would be fine. But if you do move to AMD it will leave you a base for a new, old system. You can never have to many PC's lying around.
BTW a simple Google, will convert U.S. Dollars to Euro's, or back the other way.