Series9.com and Seriesnine.com are both taken (neither is car related).
Series9.org, .biz, .us, Series9racing.com and Seriesnineracing.com are all available.
914RS.com was available, so I got it.
Series-9.com is available, but I'm not crazy about hyphens in domain names.
You guys were helpful with the logo, so I thought I'd get some input on this too.