Any good math / numbers folks around here?

Not at all. Sounds like you bought more truck than you can afford man. Highly suggest you stick it out for a few years if you can until you're not as upside down. Hopefully things turn around in the future. Look at refinancing, it might help a bit.

 

I would try refinancing as well, as others have said local credit unions usually have the best rate. Either way, see if you can put money towards the principle. If you have the cash to spare it can ease the hit on interest you are currently experiencing.