Well it seems you are interested in a very accomplished 2 channel system which may be consider at the upper end of value, not necessarily cost.
With a 20wpc power requirement I would look int tube amplification with a high quality DAC/Streamer. Search the many threads herein regarding streamers. I use a computer for streaming to find new music, use a transport with DAC for serious listening. I will one day get a dedicated streamer however likely not one in the budget range you may be looking for. Very good DAC/ streaming combo, either as single piece or as separates.
Regarding tube amplification I would encourage you check out Aric Audio. Aric make several tube preamps and amplifiers. He is very accessible via net or phone. Great to talk to and willing to advise. He also is willing to modify his products to suit individual needs. I know there are many viable manufactures however I own one of his preamps and amplifiers. Should I look to upgrade I would likely deal with him 1st.
Well, maybe not very much help for a rather lengthly response.
Regards, Mike