In fact, I thought the Carissa was rated at 18 watts, but I decised to check with Tom's website. This shows that it's 16 watts, so that's what I quoted. Tom is more interested in building his fantastic amps than updating his website, so whether 16 or 18 is correct, I don't mind - as long as it sounds great!
When Tom was exhibiting at a Hi-Fi Show at a Heathrow hotel several years ago, I took along my Avantgarde speakers for his amps to power. The general consunsus of visitors who had also heard Avantgarde's own room, considered Tom's room sounded better. Avantgarde of course were using their own solid state amps, so perhaps this explained the better sound with Tom's valve kit. Peter