It's not just graphics card...it also matters what cpu you have and whether or not you have windows 7/vista/xp.
And with the first two whether Aero is turned on or off. My laptop has a better cpu but integrated and it's on xp, so it runs mabi on higher settings than my desktop does even though mabi itself says it shouldn't be able to run it.
Just set reflection to nonexistent, fully display only your character for demigod-mode, etc. That should eliminate most lag.
Also the dds fix that one guy said REALLY helps.