D) none of the above.
I would tackle taxes with the details below, sell the car, etc.
A few ideas:
1. Cut more. Cell phones with Republic Wireless or Airphone yet? CFL or LED bulbs installed? Shopped your insurance carriers for home/car with an independent agent? Taking lunches/cooking 6 days a week?
2. Filing taxes with a home office deduction? If not, you should, assuming your husband does anything from home. You can deduct house space used for office. If his work space is, say, 10% of the square footage of the house, you can deduct 10% of mortgage interest, electric, gas, water, property taxes, insurance, pest control, on and on.
4. Don't invest in the husband's 401k at this point. Use these tools, and that money, to invest in these "less than one year" payback items listed (home stuff, CPA time, etc) and pay much lower taxes, assuming you make some jack.
5. with the tight predicament you described, I would suggest STOPPING your own 401k contribution and invest that money into these details. Yes, you'll increase taxes by 15-25% of the amount you now receive in your take home pay. However, if you stop contributing %500 per month, you'll pay $75-100 of that in tax and have $400 to make these changes (and pay taxes on hubby).
Your situation sounds like you're cutting it really close, so I would really take this an emergency and make some semi-radical changes to right the ship ASAP. Get the taxes under control, chop expenses, etc.
As an alternative, you may want to pay off one of the loans IF you will have enough to pay the taxes.
Or, finally, you may want to sell the big car, take the extra cash to closing to pay off the loan, and talk with your credit union about getting a $4,000 loan to buy a $4,000 car that you can drive for 5 years+.
Hopefully that gives you several alternatives that can fit a variety of circumstances.
As a self employed person, cash flow is king, and I have really sacrificed to kill items that cause recuring expenses so that I could profit for decades. Be careful and don't "over invest" in these ideas, but use them as a road map, as they are all critical for self-employed folks (and most others as well).