I would have to agree with all the financial advice given by the others. Don't try to force yourself into the Volt because of it's greatness if it doesn't pay off financially. Weigh the cost of maintaining your current car and if it's still doing well, then keep with it and put money aside to increase your down payment when it does come time to buy a new one.
For another example of costs, I decided to purchase my 2012 instead of leasing. I got a few options, but not fully loaded and got the car at invoice. I had a trade in worth about $4000 plus a $10,000 down payment. With 0% at 72 months I'm still at $406 a month on my payment. I checked with my tax adviser long beforehand and I qualify for almost the full $7500 Federal tax incentive as well as the $6000 Colorado incentive. I fully plan to take those rebates when I get my refund early next year, pay down the loan and refinance it. That should put me closer to $250 a month.