Hey Daren, you should be able to get a rim thats generally a pound an inch as a light weight wheel.
My last autocross car I used Konig Heliums they were 11 lbs for a 15 inch rim and let me just confirm to you the car was spin happy. When it was with its regular 17 ADR M-Sports it couldnt just break lose in anything other than 1st and then a chirp late in 2nd but with the Konigs and much stickier rubber I would be having issues with traction in 2nd and getting chirps and slides in 3rd.
That being said its always expensive but if you keep an eye out on NASIOC.com there are loads of high quality wheels at decent prices that will fit our cars