I just bought and demoed the Midas 502 V1 and I made a comparison with the Burl B1.
I'm extremely (positively) surprised with the results, considering the cheap price.
I preferred to buy version 1 (and not the current V2) because it has the transformer on the output which returns a different color. The review is in Italian but you can still hear differences between the two modules.
I hope it will be useful.

https://youtu.be/zTgRY2WAPck