Luxman Lv103 Hybrid transformer question

I just picked up this cool little hybrid unit but it came from Asia and has a basic looking external 500W 200 to 120 volt transformer.

Any suggestions as to whether to leave it as is or swap out the internal transformer much appreciated.

btw - tremendous sonic clarity compared to by old Bryston 3B on accoustic/vocal music but she does struggle with my AC/DC... bass is clear but not very prominent.