Help getting a Tube Amp

I have a pair of Monitor Audio Studio 6 Loudspeakers 88.5 db 6 ohms min. . I haven't used them for a few years but I would like to get a good tube amp and a sub woofer. My room is 11.5' wide x 17'long, I was thinking of an 845 amp is this enough power?
If an set isn't enough power what is ? I listen to mostly rock and sometimes classical.
I never used a sub woofer so any help with a sub for 2 channel only is appreciated.
Thank you
Abill