Here's your situation as you've described it:
Code:
Debts
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$ ? @ ? % 1st Mortgage
$ 15 000 @ 7.5% 2nd Mortgage
Assets
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$ 10 000 Emergency fund
$ 5 000 Car fund
$ 10 000 Company stock
$ 10 000 Tax refund / bonus money
Pending Expenditures
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$ 10 000 Replacement vehicle
The solution seems clear to me. Cash in the company stock. Combine it with your "Car Fund" and pay off the piggyback mortgage immediately. Then when your tax refund and bonus money come in, buy the replacement vehicle. If either vehicle dies before then, use your emergency fund to buy the replacement vehicle, then replenish your emergency fund with the tax refund / bonus money. No new debt required at all, no need to (permanently) sacrifice the emergency fund.