Portable test amp
This may be a day late and a dollar short, but if they are still available, you can get just about everything you need to make a very portable stereo amp that actually has pretty good specs and is dirt cheap. It is a great way to test speakers / drivers when out at a flea market, boot sale, or whatever they may be called in your neck of the woods.
Bear with me and hear me out. Go to your local Dollar Tree, if you have one near you. Look in the aisle where they have the "Electronics" and see if they have the little round battery powered amplified speaker available. If so, pick up 2. While there, grab a 3.5 mm audio cable. If you wish, grab a USB cord and a USB wall charger. (More on that later)
Now these amplified speakers claim hi-fidelity or some crap like that, but the tiny little driver inside the plastic "ball" case bites the big one. About the only good thing on them is the magnet. Go ahead and put batteries in and connect it up to a source - your phone works well since it was designed with that in mind. Play some music. Ugh! Horrible.
But Wait! There's more!
Open up the case (3 screws), disconnect the speaker leads and connect them to a real speaker. You'll be amazed that this $1.00 amp can sound so decent, albeit in mono.
If all you would need it for would be to test a speaker while out shopping at a thrift store or some similar situation, then all you need to do is extend the leads and button it back up. Dirt cheap and handy. Could save you a bit of cash by verifying that $100 speaker is good or blown.
Here's the next level: take the little balls apart, remove the amp boards, (they are really small) and set them down so you can see them with the input jacks on top. There is a left, right, and ground trace comng off the jack. On one, cut the left trace somewhere between the jack and the input capacitor, then do the same on the other board, but on the right trace. Now, tie the battery positives together, then the battery negatives together, then solder a pair of wires from the right input to the right input from board to board, between the jacks and the cut, and the same with the lefts. Connect power, speakers, plug in the input, and you are ready for a surprising listen. If you've purchased or have an old USB charger/cord, cut the unused end off and connect red/red, black/black and you'll get 3W/ch. Not bad for $2-$5, depending on how much you have to buy. (If they are still around)
Here's a video showcasing it's abilities.