Ah, OK, that does make things more complicated. If cars cost the same amount from a dealer as on Craigslist, then it would be simple. I would recommend selling your car right away, and financing a less expensive, more fuel-efficient car at the 2.64% interest rate. This is a clear win over your current situation, since you'll be paying interest on a smaller amount of principal, so the total amount you pay in interest to the car company will be lower, plus you'll have a smaller car payment each month, so you can redirect the difference to paying off your higher-interest rate student loans even faster.
What makes it tricky is that it typically costs about $1300-1500 less to buy a car directly from the owner than buying an equivalent car through a dealer, and buying directly from an owner generally requires paying in cash. (For example, a 2009 Toyota Yaris in excellent condition has a KBB of $8691 for a private party sale, but $10,016 through a dealer) Normally, this is a win-win, because you'd want to pay in cash anyway so you don't throw away money in interest, but because of your student loans, for you, paying in cash is equivalent to borrowing the money at 7.35%. So, which is better? Borrowing for the car at 2.64%, or borrowing for the car at 7.35%, but paying $1300 less? The short answer is that it depends how long you're going to be borrowing the money for. The break-even point for $10,000 at 2.64% vs. $8,700 at 7.35% is somewhere between 6 and 7 years, with shorter terms favoring the lower principal, and longer terms favoring the lower interest rate. You don't say exactly how much you owe on your student loans, but given the huge amounts of money you're throwing at them (awesome job, by the way!), you're probably going to have paid them back in considerably fewer than 6 years, so you may be better off paying cash rather than financing. This would basically involve paying only the minimum on your student loans for four or five months to save up the cash to buy a car on craigslist.
Of course, there is one other option, the one you mentioned in your original post--keep the current car until you've paid off your student loans and saved enough to buy a car in cash and then sell it and buy the used car. So how to decide between these two?
If you keep your current car and buy a 2009 Yaris once you've paid off your student loan, the total cost of the Yaris would be the total you'll pay in car payments until you pay off the student loans, plus the cost of the Yaris at that time, minus the difference between the selling price of your Accord and the amount you'll owe on the car loan at the time. So, for example, if you could pay off your student loans in two years, you would pay $7200 in car payments on the Accord, a 2009 Yaris would probably cost $6000 at that point, your Accord would be worth $10000, but you'd only still owe $6300. So you'd net $3700 on your car sale, for an additional out-of-pocket cost for the car of $2300, or $9500 altogether.
If instead you save up now for the car, imagine it as if you if you were paying your student loan payments as usual, but instead were taking out $1910 loans each month for the next 4 months at 7.35% so you have enough to pay for the car. Of course, you'll be continuing to make payments on your Accord as well during this time. You'd sell the car, net a small profit (by this point, it should only be worth $12,667, but you'll only owe $11,910), and buy the 2009 Yaris with the "loan" plus the sale profits, which will only cost $8400ish at this point. Then you pay the $7640 loan back at $300/month (the $300/month you were directing to your car payments before--in reality, this will mean you'll be paying $2200 towards your student loans). You will pay off your "student loans" after 2 years (during which time you will have spent the same $7200 in car payments), and still owe $2064 on the "car loan", which you would then pay off the following month. Note that this means you'll pay $7200 + $2300 if you switch later, and $7200 + $2064 if you switch now.
So, basically, as best I can figure, if you have two years left to pay off your student loans, you'd get a net savings of a couple hundred dollars from saving up and buying the car now rather than later. Of course, it will be different if you have more or less time left on your student loan, and obviously there are a lot of assumptions I'm building into the model, so I'd be tempted to call it more or less a wash and it just comes down to which car you'd rather have for the next two years. Of course, if you drive much at all, the difference in mileage alone (31mpg vs 24mpg) will save you a ton of cash (If you drive 31 miles a day and gas is $3.00 a gallon, you'll be spending $3.00 on gas a day instead of ~$4, for a total gas savings of $730 over the two years). So that plus a small cost savings on the car itself would lead me to favor buying the car now rather than later.
Let me know if you have any questions about what I did, or if any of my assumptions were way off (about how expensive of a car you want to buy, or how much more you actually owe on your student loans). Also, to make it not crazy hard to calculate, I assumed that all of your student loans are at 7.35%, as opposed to some at higher rates and some at lower rates. I can imagine situations where it would make a difference (for instance, if you have two more months to pay off the last of your 12.5% loan and then everything else is at 5% and below, I'd guess you'd want to pay off the high rate loan first and then save up for the car), but I didn't consider any of that. Hope that helps!