Any way a preamp can drive small speakers?


Does a preamp have enough power to drive small speakers on its own?
Could preamp output be mated to an impedance adjusting "black box" to bypass a main amp?
I've seen many preamps (Cary comes to mind) that look like they could do it.
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I have a McIntosh C34V pre which I bought new (and it still looks and sounds the same as day 1) which has a built in 20W/ch amp. While designed for headphones, Mac included speaker terminals on the rear of the pre. A nice, handy little touch.
Thanks for all responses!
I know this query is kind of off-the-wall but thought it would be interesting.
If you've ever seen the guts of a BAT 50SE preamp, you'll know why driving tiny speakers shouldn't be unreasonable.
I went to a Threshold demo many years ago and the rep had hooked up a Threshold FET 10e to small speakers to demonstrate the robustness of their separate power supply.
This particular preamp had a very low output impedance and put out a few watts of class A power into the speaker load at 8 ohms instead of the typical amp loak of 50 k ohms.