At that price range, most graphics cards aren't really worth it. They tend to be mostly cards designed to add more monitor outputs, not for gaming. This is further complicated by the fact that your computer won't allow us to use full-size graphics cards, and the PSU probably won't output enough power for anything particularly good.
If you do insist on adding a card, there seem to be a few GT 740's around that price range or cheaper, but you have to make sure to find a low-profile version so it will fit inside the case. I'd be surprised if these can't play Sims games at 900p, but I think I recall there are several versions of the 740, so some of them will perform differently.
I would also consider looking for used stuff. You can probably get a 750 or 750 Ti, which might still work if you can find a low profile card, and will give you noticeably more power. It won't be easy to find a card that will work very well in that case, though.