I'd swap the hdd for this:
http://www.overclockers.co.uk/showproduct.php?prodid=HD-226-WD
EDIT: and if you like you could get an aftermarket CPU Cooler.
There, swap some of the parts for the same ones from other... places. You also need a couple of crossfire bridges, and i wasn't sure if you wanted a mouse and keyboard.
i figured the psu would be the overkill for 1 graphics card but i am planing to add another ati 4890 next year so i am actualy doubting if the 850 psu is enough? i am not much in computers so the suggestions are always welcome.TBH, with such a lovely system its a shame its only going to be running a TN 20" screen.
PSU is overkill, get this unless you plan of Multi GPU - in that case get this.
I agree that a chance to a WD Black 1TB would make sense - much more consistent performance.
Antec 1200 is a good case, might want to have a look at this one too.
Don't get the stock 4890 get the xfx 4890
i dont see the difference between retail one and the xfx, why should i get the xfx which is priced 20 squid even more?
***EXCLUSIVE Premium Priority 2 Year Warranty***
In the unlikely event of your card failing within 2 Years, OcUK will replace your card with a brand new one, pending testing within our standard RMA terms and conditions (http://www.overclockers.co.uk/support.php)
850W will be fine for a dual 4890 system, you could probably get away with 750W, but 850 will give you loads of headroom.
The awesome warranty deal with OCUK/XFX: