Reviews always mention the resolution they are testing at, usually prominently with every benchmark so I'm not sure what you are talking about there. Your resolution is actually rather low by today's standards and even a cheap card can handle it quite well. For your reference when looking at benchmarks your resolution is equivalent to 1280x1024 which is a more popular resolution for testing.
The cards rolli listed are overkill currently but not a bad idea if you want something that will last several years or if you might upgrade your monitor. They start around $150 however and cards closer to $100 like the HD4850 or GTS 250 would also be very good and let you max out the settings in almost every game around at the moment.