I will expand a bit on the power vs ohms thing.
Watts is a measure of power, it is how we measure the amount of power we have to do some work, which in this case is move the driver cone in an out. little drivers in the tweeter require very little power to move, big cones used for bass are heavy and require alot of power to move.
We calculate watts as Amps*volts.
Ohm's Law is Volts = Amps*Resistance.
What this means is that when you divide the resistance of your speaker in half (go from 8ohm to 4ohm), the amperage has to double. 4 ohms is a very low resistance, very close to a dead short. An incandescent light bulb is about 9ohms, and consider how hot they get.
I say all this to underscore why people are recommending an amp that can handle the low sensitivity of your low resistance speaker. Low sensitivity speakers can be very demanding on amps, and they can die.
I suggest that if you can not find your way into at the least a reputable ChiFi brand, see if you can round up an old receiver or even an AVR. These will usually have some circuit protection built in to protect your speakers in the even that the amp overheats.