Looking at a new video card, but know just enough to do something stupid, so seeking advice!  Current system is a Dell Inspiron Pent core duo E7300, 4GB DDR2 SDRAM with AMD radeon HD 3450 PCIe card ( I have made the recommended ATI adjustments for BHaH), Vista 64 bit.  Have the sliders at 2,2,1,2,1, getting frame rates in the 30's but flying in the rain makes it stutter and I'd like to get those sliders up!  Anyway, looking this card on newegg (since its $60)  
  
XFX PVT96OZDFU GeForce 9600 GSO 1GB 128-bit GDDR2 PCI Express 2.0 x16 HDCP Ready SLI Supported Video Card  
  
Is this a good upgrade for me, will it fit in my slot/case, will it improve my BHaH experience, do I need anything else (RAM, dual carbs, headers, etc...)?  If not a good idea, any suggestions under $100 (the "sneak it by the wife" threshold  ) 
  
Thanks for any help!