I too was going to mention the plug from Radio Shack that has the 
multi-connector posts built into the handle.

I have one of these plugs, which I find to be the handiest thing since 
sliced bread.

I have powered up to a 50 watt rig through the cigarette lighter with 
no problems for almost as many years as there have been 50 watt solid 
state 2 meter rigs.

The only failure I ever had was when I was using a plug that had been 
soldered onto the power cable for my then relatively new Icom IC22S, 
which was a 10 watt rig. The connections inside the plug itself 
shorted, and shut down whatever was on the same fuse as the cigarette 
lighter.

I replaced the fuse, and then replaced the plug with a more industrial 
strength model from a hamfest, and had no more problems.

That said, I wouldn't try a 100 watt HF rig, and probably not even the 
newer 75 watt class 2 meter rigs with this arrangement.

But Chris should have no problem using the cigarette lighter to power 
the amplifier he described.

Just in case you do need to know in a hurry sometime later, though, 
try to determine, either from the automobile owners manual, or from 
the fuse block itself, the value of the fuse for the cigarette 
lighter. Also, be aware that the extra socket for cell phone chargers 
and other accessories may have a lower current rating, and thus be 
fused with an appropriate lower value.

Happy mobiling.

Mike Duke, K5XU
American Council of Blind Radio Amateurs