A 650 ti is a video card with a little more power than the one in the computer you listed, it would be a good improvement. All that video card in the computer you listed is good for is bwosing the internet really
My budget is £400 But I can maybe go a little higher. I am in the Uk so need UK PCs, it is for my 15 yo, she won't be gaming on it much she has xbox for that but will want to play the ones mentioned.