Sell stocks to buy a new car or just finance?

I have about 100k in the market. I have been very responsible. I have a 5 month emergency fund. I max out my Roth every year. No 401k through my biz, it's crap. I drive a Pontiac Vibe from 2005, which I love. However, I kind of got the itch to buy a new car at 30k. So, cash for the whole thing, or is the loan at 3.5% a better option. I suppose my 30k in a sp500 would do about 7% a year. Opinions plz!

EDIT: Thank you for the replies. Great advice here. I have decided i will leave my equities and investments intact. I am going to wait for a little while, save up cash, and if interest rates begin to climb, i may go ahead and just finance. But i am surely going to wait, probably a year. Thanks you all!!! GO INTERNET! HAH