Not sure I agree with Oli. (though i’m not an expert)
what os are you running? adding 2gb is likely to give you a good improvement. Assuming you have a spare slot, you may be able to pick up an extra 2gb for next to nothing, depending on the type.
Same with the GFX card. Yours maybe old, and slow, but might be enough for what you want. If its too slow, and new faster one could probably be had for £20-£30.
Might even be worth looking at upgrading the processor. Again, because your looking at old technology, sometimes these things can go for throwaway prices. Check out what you MB can support and head on over to ebay.
Lastly, it could well not be your computer that is slow. Could be your connection to your router, your internet connection or redbull website.
Oh, and if you do end up upgrading the mobo, you may have to upgrade the PSU too. Connectors have altered over the years.