This is the exact amp I received as a Christmas gift and referred to in an earlier post. I got the "Monoprice" hybrid tube amp, as it is called. About $140.
I was disappointed as I knew right out of the box it was gonna be weird, but felt for my generous but technically-challenged brother, who bought it. Right out of the box it had a smoked tube, but fortunately I had a pair of old 6BQ5's (EL84) I threw in and got sound. I also ordered two Russian 6N2P (6ax7 equivalents) from The Tube Store and I think that further improved the sound as I originally heard it with the Chinese tubes in. Or was I just expecting the improvement??
Bottom line I replaced all the tubes and it puts out sound. It is strange and probably worthless but it was a gift so I'm trying to find a place for it. I pulled tubes while it was operating to see if they were totally bypassed or otherwise bogus and the sound stopped, so they are somewhere in the circuit. I saw the video and he pretty much trashed it I think it probably ends up going through some kind of Class D amp for the power side. I also think they bump the voltage on the 6N2P's to make them glow brighter than necessary to give that tube glow....wild stuff.
I just don't think you are going to get into anything really tube, vintage or new, for less than $500 or $600 and probably more than that unless you find an estate sale or a fluke at Goodwill. A real tube amp for like $140 was just never, never going to happen.