"45 fps" is fine sure, but with what levels of detail, what resolution, and with what kind of FSAA and ansio filtering?
I find the game looks a TON better to me at 2x FSAA for example, and luckily I seem to be a bit cpu limited because at 1024x768 I get almost the same framerate with no FSAA/ansio as I do with 2x FSAA and 2x ansio filtering. The trees, horizon, and hangars shimmer and "crawl" much less with FSAA turned on.
I used to run AH at 1280x1024 and no FSAA but found that the sweet spot on my rig (athlon XP 2000+ and GF4-4200) seems to be 1024x768 with 2x FSAA.
Get a better vid card, and you get better graphics in addition to the pure framerate. If you want framerate uber alles, you can get a whole lot more by turning all the sliders all the way down, decrease texture size, and move the horizon in way close (shift-f4?) but it'll look pretty smurfy.