Sound advice man, appreciate it. I bought it 3 years ago with 22k on the clock for $14,400, a little under private party blue book. I got into a 5 or 6 year loan and have pretty much just made minimum payments.
You've been making payments for 3 years and you still owe $6k on a 12 year old vehicle? Something doesn't add up, either you paid way too much for that 4runner, or you had another car you were upside-down on and rolled that into the loan, or your payments are too low, or your interest rate is way too high.
With gas the cheapest its been in years my recommendation would be to curtail the road trips and get that 4runner paid off ASAP. Once it's paid off you should be able to sell it for a decent price given the low mileage, and buy something you want.
I understand "vehicular ADD", I get it myself. But I think your "plan" is just going to result in you being deeper in the black hole of debt. As a good friend of mine once said "the cheapest vehicle is the one you already own."
As for not having "AUX" in your 4runner, for a couple hundred bucks (that is to say, for less than a car payment) you can put a great double-DIN stereo in that will have AUX, USB, Bluetooth, iPod controls, etc. Get it from Crutchfield and install it yourself, it's super easy on the 4runner (I did it, so it must be easy.)
Seriously, if you're on a budget, hold what you've got until it's paid off. Make sacrifices elsewhere in your budget to get that 4runner paid for and once it is, you'll be in a much better position. If your 4runner still has under 100k I'll bet you could sell it for 10 grand in SoCal even with 2wd.