Read this first before you do something stupid like buy 17" rims and race on them. I already did it, thats why I can call it stupid.
Also take into account that the average 17" tire is something like $130. You can buy a 15" tire for about $70-80 and a 16" tire for about 90. You will be killing a tire in 1 season. Plan on buying shitloads of them.
You don't need forged featherweights. Something like a Rota, Konig or the Team Dynamics Pro-Race wheels are popular with the autocross crowd cuz they're light strong and cheap enough that if you trash one, you can get another and not break the wallet.