Dumb lo-fi question.

I have an old (1980) Toshiba receiver that I use down at my cabin. Have been pondering a slow....very slow...upgrade path of that lo-fi system and I have a question. The receiver is rated at 25 wpc. It has two sets of left and right speaker outputs. In other words it will drive 4 speakers. Does that mean it will send 25 watts to each of the four speakers or 12.5 watts to each of the four speakers?
Yeah depends on many factors of course - much like millercarbon wrote. You really need to know how much power your speakers will draw from your receiver. The speakers have a sensitivity rating and an ohm rating, which is a good start. Just follow the passage from millercarbon about that ohm rating and find the sensitivity rating on the speakers.  Also, older receivers tend to need parts like capacitors.... so it may need serviced too!!
Thanks guys. That's the info I needed. 
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I guess a better way to phrase my question is did these old receivers ever come with two separate amps inside...one for speakers A and one for speakers B. I assume the answer is no.....but it would have been a neat feature.
I believe you are assuming correctly. Receivers of that era, and probably now also, would parallel two sets of speaker terminals.  Generally, most speakers, I say most, not all, run a nominal impedance of 6 to 8 ohms. If you run four speakers that are 8 ohms nominal (average), your total impedance would be approx. 4 ohms. The receiver might put out more than it's rated power of 25 watts per channel, which should be ok for that receiver. If you have the owner's manual they might caution you about running four speakers with impedances lower than 8 ohms. To low of a speaker impedance load, and you will wind up frying that receiver, especially if you crank up the volume.

I have a Harmon Kardon receiver with the same capability to run  2 sets of speakers, and it pretty much told me what I have told you.
Good luck!