He wants passively cooled, which rules out anything higher than a 7600 GT really in the 7 series, and there's very few passively cooled 8 series cards. Also, he said he didn't want ATI. Here's a passively cooled 8600 GT that should fit the bill nicely.
As for monitors, you should probably try to match whatever monitors you already have. Then you'll be getting performance you're already comfortable with. However, if this is not possible, then just get any monitor with a response of at least 8 ms and the highest contrast ratio you can find. All this might be hard to fit into a 250 GBP budget, though.