PS I wish Elekit would make 300B monoblocks. I'd buy and build them right away.
@lalitk, I built an Elekit TU8600 300B amp with substantial upgrades (Takman resistors, Mundorf caps, Lundhal power transformers). My source is either vinyl or Tidal streaming. In vinyl, I use a Technics 1200 GAE, Manley Chinook phono pre, and an Audiotechnica ART9 MC cartridge. With Tidal, I pull the stream through a Bluesound Node 2 and feed it to a Doge 7 tube DAC or an NAD M51 DAC. I also use a Schitt Freya as a control/preamplifier because the Elekit only has one set of RCA line level inputs. My loudspeakers (in the SET amp system) are the newly released Klipsch Forte IIIs. I have decent cabling but nothing crazy (Mogami speaker wire, soldered DIY to Cardas spades, and Chord RCA cable, several DH Labs cables (RCA and digital).
For the subwoofer, I'm using an REL T9i. It's dialed in very light and smoothly so as not to interrupt anything. I've set it up with software and a special mic, BUT it always sounds better set by ear using tracks like Neil Young's "Out on the Weekend"--whereby I tune the sub to the kick drum to make it sound as resonate and real as I recall from playing music with others. That track gets me closest to proper than other setup methods.
+1 on the Line Magnetic reference above. I was looking at them last week and was very very tempted just to give it a try.
I should also note that even though my speakers are upper 90s in efficiency, I have a big room (well, big for me and bigger than I ever dreamed)--it's 15' wide by 23' long with 10 foot ceilings. The acoustics are really nice without alot of "nodes".
I should also note that when I use a Primaluna Dialogue HP integrated or NAD m22 Masters amp there is no need for a subwoofer because there's so much grip on the large drivers. But 8 watts a side is a little light for this room. I don't like to listen that loudly anymore and prefer the accuracy and romance of the 300B SET. But the REL brings everything into focus. If I put decor over it or obscured it from view somehow I don't think anyone would say, "oh, I hear a subwoofer". It's set to do a vanishing act and I really use it to tune the room as opposed to pounding out bass or what have you.