you should also look at this:
http://www.commutesolutions.com/commute-cost-calculator/you say you can keep your money in the market. that is a plus.
I say you cant afford it because you don't have any other cash you can use but cash that is meant for 10-50 years from now. you are holding your future retirement as collateral to purchase a vehicle.
that means you can not afford it.
maybe some numbers would help.
how much do you make now?
how do you currently get there
what is the raise
how far would you have to travel?
what type of vehicle are you looking at
what is the interest rate on the retirement loan?
what have you been pre approved for a a credit union like DCU?
how much cash do you have right now?
how much would, gas, insurance, and other stuff cost?
if 30% more minus the cost to own minus time loss are a wash this isnt an investment. do not forget depreciate. you do not get the value of the car= the amount you pay