2560x1600 Dolphin Eye candy

[Kodiack]

Having 4x the internal resolution and 4xSSAA makes for 16x the internal resolution. Knocking the internal resolution down to 3x and bumping SSAA up to 4x should give you 12x the internal resolution. It will still potentially lower performance compared to what you're using now, but it should be significantly faster than 4x+4x.