Get rid of AA, then reduce grass distance or get the Shorter Grass mod. Big performance gain right there.
I run Oblivion at either 1280x960 16xAF 16xQ SSAA or 1600x1200 16xAF 4x SSAA, with Qarl's Texture Pack 2, Natural Environments, Cities Alive at Night, Phinix Waterfix, Qarl's LOD Normal...