Thomas was our lead singer and rhythm guitarist and back then, he mainly played chugging power chords with zero effects (and I mean zero!) with a relatively undistorted sound (with a humbucker Les Paul of all guitars, an unlikely choice for a rhythm guitar as he would realize much later, but as a 20-year-old he liked the silverburst fin of it, when it invariably turned green he was aghast and sold it
). For that, the Hiwatt was reliably fine. But as his playing matured (he plays more in a Keith Richards vein these days), the limits of the Hiwatt combo became glaring. It didn't sing and it wasn't creamy, no real texture too, just crude amplification, doing what it said on the tin: high watt!
I always thought Townshend's solo sound pitiful - there I said it.