I have a Blue circle BMPH integrated connected to mine. I agree though that you should be able to go for high quality/low power tube amplification. Sandy Gross demonstrated the STS for a Stereophile reviewer with a Cayin A-50T integrated. At CES 2008 Definitive used Pass Labs XA 100.5 monoblocks to demonstrate the ST. So they seem to feel that lower-power lower-priced tube amplification works well or medium power expensive solid state works well with this line of speakers.
