pop into WHSmiths and have a read or buy this months custompc mag. have good review of all middle to top range graphics cards (27 in all).
the one you are thinking off will not be much good for todays games by the way, if that is why you are upgrading. recommend either ATI's 9800 series or nvidia's 6600gs series but are 3/4X dearer than the one you are looking at but best for games on an AGP mobo.
Have a look here click here the 9550 isn't there but the 9500 is and the 9600 so it would probably be somewhere in between them, it'll give you an idea of what you're getting for your money. This is a cracking card for the money click here around about the same as a 9600.
Should mention in case you don't know. When you get into faster cards. The 5600 I gave you a link to is one of them, they require a power connection on top of the power they get from the AGP port so make sure your power supply is up to it. I'm not sure if the Sapphire you gave a link to requires a power connection as well or not.