Very low settings/resolution on the 9400GT. On the GTX 460 you should be able to max it out at 1600x900. However you really need to make sure your power supply can handle any card you might buy so tell us the brand/model. If you don't know it should be listed on a chart on the side of the PSU inside of the computer case. The PSU is the part the power cord plugs into.
This is very nice deal on a 1gb GTX 460;http://www.newegg.com/Product/Product.aspx?Item=N82E16814187115
There's nothing under $200 that is notably better really. If you are ok with mail in rebates then this HD5870 is a good buy and under $200;http://www.newegg.com/Product/Product.aspx?Item=N82E16814125316
Or if you are ok with overclocking/rebates/going slightly over $200 then this GTX 560 Ti is worth considering instead;http://www.newegg.com/Product/Product.aspx?Item=N82E16814162074
Both of those cards are approximately 30% faster than the GTX 460 at your resolution on average and the GTX 560 Ti can usually overclock up to 1ghz or 20% more.