I would recommend buying Race On DVD version, which includes STCC (NOTE ONLY THE DVD BOXED PACKAGE INCLUDES STCC) and activating it to your Steam account.
Then also getting STCC2. That way you not only get STCC content from both games but you get the Race On content/tracks too!
Currently Race On DVD can be purchased on Amazon for Less than £6 delivered in the UK..
http://www.amazon.co.uk/gp/offer-li...p?ie=UTF8&qid=1307224021&sr=8-1&condition=new