Yes, better caps will make the sound better and yes, it should change it some depending on which caps you use. Most all caps, resistors, wire and etc. change the sound sometimes for the better and sometimes better but not what you was wanting. At first I would definitely change out the power (electrolytic) caps and increase them some if needed. That will bring some life back into your system. Then you upgrade the caps in the secondary power supply and maybe diodes depending on what kind are in there now. After that you will need to decide what change you looking for? More detail? More bass? Better mid-range and then choose the right caps to get that done, including maybe upgrading some resistors if needed.
Randy