Well the LG BD390 IMO is not comparable to the Oppo 83 at all. If youre looking to compare LG BR with a Oppo product it must be their Oppo 80 model.
Here in Denmark atleast, the LG BD390 priced around 1800 DKR and the Oppo 80 is about 3000 DKR region free. The Oppo 83 is 5-6000 DKR region free.
What makes the Oppo 83 and the 83SE for that matter, so great; is what inside tech you get for that price. And yeah the build quality is in another league too. Not B&O style, but its good.
By dvd upscaling, I mean that the signal the BR player sends to the tv is good. Not how the tv handles lets say a standard dvd signal or something like that. There are various dedicated chips for upscaling DVD's to HD resulotions, and the one used in Oppo 83 is amazing. Atleast, that its available in product in that price range. In other words, the better the upscaling the better the picture you will get.
I don't know if the LG BD390 is in B&O puc table, but Oppo is. Otherwise if youre going for the LG, and its not in the PUC table. I'm sure your dealer can generate a table for it - then the handling of the LG from B&O is as good as if it was an Oppo, or something else in PUC table for that matter.
Best regards