Speakers under $700 for 8W Per Channel Tube SET

The first thing you should look at is the efficiency of the speakers. Most will not give enough volume; I would look for ones in at least the low 90s and preferably higher.

With that room volume you will probably want 95 dB+ but much depends on your maximum listening "volume", minimum impedance, impedance variation (curve), type/presence of crossover and your listening position in terms of distance from the speaker. I have a second system moderate size bedroom (maybe 10 or 11 x 14) with the speakers on the long wall. They are front-loaded, single driver zHorns at about 93 dB efficiency and I listen to singer songwriter/folk/acoustic blues, etc, at low-moderate volumes. I tried a Berning microZOTL (which is 1-2 wpc) since I was mostly using headphones and found that it works in that situation. I'd like to have a bit more gas but since the music does not have much deep bass and the volumes are nowhere near "realistic", its just fine. Your MMV.

Coincident or Klipsch