Whilst I agree the PSU can easily be replaced, just replacing the PSU is not a good idea,
Some Caps I would recommend on the Cap board as well as a general check. Also if you use the new PSU version you need to modify the display board to have a new reset chip.
If you are in the UK we can look at your item, we may be able to consider a 2-day service as we always soak test the products before shipping them out.
800 is always a better player than the G9x players, the clock and highspeed interface on the 800 is far better.
Regards
Edd