Ok, according to online resources that dell came in two form factors a slim chassis, and a tower chassis.
Now I'm sure the system is stock. Which limits what you can put into the chassis as a 25W video card.
So a 6450 should be fine (28ish watt TDP)
I just can't imagine playing world of warcraft with a 6450. ( I play the game as well)
But all in all a 6450 is a few times more powerful then a 2400.
(the only reason I posted the asus one is because it comes with a low profile bracket. You can obviously pick whichever manufacturer you want yourself. I just know this one will work with either chassis of dell you have. And also asus doens't make bad products :-) )
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