Even if the transformer looks like a piece of crap, it will very likely improve the unit's sound and not degrade it as you fear.
That has been my experience with every digital source I have ever used in my home. Isolating the electrical supply with a transformer has opened up the soundstage and improved definition significantly. Your transformer is meant to step the supply up from 100V to 117V but it will have isolating properties as well. So IMHO you're in luck.
Try the connection both ways and see if one is better--that is , with the transformer plugged into the wall or into the Powerbank.
As for upgrades, you may not need one (some very good-sounding transformers don't look very impressive). However two good names in aftermarket isolation are Topaz and Xentek.
That has been my experience with every digital source I have ever used in my home. Isolating the electrical supply with a transformer has opened up the soundstage and improved definition significantly. Your transformer is meant to step the supply up from 100V to 117V but it will have isolating properties as well. So IMHO you're in luck.
Try the connection both ways and see if one is better--that is , with the transformer plugged into the wall or into the Powerbank.
As for upgrades, you may not need one (some very good-sounding transformers don't look very impressive). However two good names in aftermarket isolation are Topaz and Xentek.