Yamaha Psr e333 doesn't sound as good as my psr f50

by Steve
(Sheffield england)

Hi I have a psr f50 yamaha keyboard and but It doesn't connect to pc.

So I bought 2 a psr-e333 and a psr e413 but they both sound terrible at side of my psr f50 and for the life of me I can't make them sound has good they sound as if my ears have popped the tones are not half as clear has my psr f50.
Is there a keyboard that sounds like the psr f50 which will connect to pc via USB or midi ect.
Or is there a way I can get the psr e333 to sound like my f50.
Hope you can help this has been bugging me
Thanks regards steve