Should I mod my original MHDTParadisea or uprade

How/where would you have it modded? For the money, the quality and part count is high on their products. Personally I preferred the DIY Paradise USB Monica. If I were you I'd be collecting different tubes for it to try. The tube (forget which) is not intended to be used as a high fidelity audio tube. I went through many tubes (I am lucky as a close friend is a tube dealer). Surprisingly, the tubes he thought would be the best (WE, RCA) weren't. The one I did like was a re-branded give away. If my memory serves me correctly, most of the tubes had euphonic microponics. Some tizzy, some with dark bloated bass ect... FWIW, at least 8-10 tubes were tried, even multiples of the same vintage NOS WE. All were different, most bad.

Jax2,
Yes I do mean tube rolling in the Paradisea. The Monica is a SS USB design. I am not saying that the Monica is all that great, but that the Paradisea didn't have the PRaT that the Monica had, although the Paradisea had a little more detail if I recall. FWIW, all of the tubes I tried were tested by a very finicky retailer (name with held) that has a very strong reputation in audio circles. The point I am trying to make is try as many tubes as you can. The "stock" one ranked about 3rd.