I have a stock 5400ES and a ModWright 5400ES. There is quite a jump in sound quality from a well-mastered SACD over Redbook with the same material on the stock 5400ES. Not subtle. I would say the stock 5400ES is a good Redbook player and a very good SACD player.
The MW 5400ES is in a different league and Redbook is very close in sound quality to SACD. The MW mod improved the Redbook sound quality tremendously and the SACD quality significantly but not as dramatically IMO.
Tidal is great but sound quality is obviously dependent on the streaming gear and the DAC. It takes a VERY good music server and DAC when streaming TIDAL to get close to the sound quality of the MW 5400ES with Redbook.
My computer audio DAC is not MQA capable, so MQA titles on Tidal are a mixed bag. I find no more correlation between improvement in sound quality of the MQA version vs the non-MQA version than I find from one non-MQA title to the next based on recording/mastering quality. All MQA versions are remastered by necessity to embed the MQA packet and the sound quality of the remastering varies greatly just like mastering/remastering quality of non-MQA titles. There are some real sonic stinkers in the Tidal MQA library just as there are for non-MQA versions. Some titles sound better in their original non-MQA version.
Again, without a MQA-capable DAC, titles designated as MQA on Tidal do not guarantee a better sounding version than the original IME. It depends on the quality of the MQA remastering.
Dave