+1 on Quicksilver. These amps are incredible value. I've owned tubed Cary, Audio Research, McIntosh, but love my Mid Mono's the most. They drive my 90db efficient KLH 5s to sufficient levels in my 15 x 18 ft room. Believe it or not, they drive them and previous Snells and Harbeths Compact 3s with better bass than a Belles SS amp I had that had 150 WPC. If you want to really raise the roof, you likely need more power but remember, double the power (in this case going from 40WPC to 80WPC) will only give you an additional 3db of volume. I listen mostly to Jazz and Folk and Indie stuff, If you want to crank heavy metal to high volumes, then suggest you stick with a warmish sounding solid state amp, possibly MosFet with 150 -200WPC and use a tubed preamp as other posters have suggested. Personally I run tubed preamp and power amp and would have it no other way.
The Quicksilver amps are super well built and in your price range you can buy new and not worry about breakdowns. My previous amp was an older Cary. It blew an output transformer on one channel that my local tech replaced but warned me that that was the last one Cary had in stock. I sold the amp as I didn't want to wait for the other transformer to go and then end up with a costly paperweight.
You can use numerous output tubes on the Mid Monos, but EL34s, to my ear, sound best. That is a good thing as they are more plentiful and less costly to aquire when you want to retube. And to get the most out of these or any tube amps, you want to upgrade the tubes beyond the standard Russian/Chinese tubes most manufacturers supply with their amps these days, although Mike Saunders at Quicksilver does have some decent older NOS Tesla tubes that get you part way there.