25w rms into 8 ohms is 50 watts rms into 4 ohms or 100 watts rms into 2ohms.
Alternatively, 50watts rms into 4 ohms is 100 watts peak into 4 ohms.
And that's before you start messing around with distortion figures. It's not hard to make a 25w rms 8 ohms at less than 0.1% distortion between 20Hz and 20kHz amplifier into a 500watt amp.