Silvias have the same shape head lamps as S13,MK3 supras, RX7, etc
Almost any jap car with pop up lights.
I used to have a set of cristal clear lights on my s13 witch are pritty good and cheap. From china on Ebay.
As for fitting higher watt lamps you will draw more current and could melt the wiering loom to the lights incl the Switch.
I think the problem could be the reflective part of the lamp getting dull or coming off, or not anuf power getting to the lamps. Bad earths!!!
Had bad lights on all VW I have driven as well, so a electiction friend came up with the Idear of fitting larger cabels to the head lamps and using the old system just to switch them on via a relay.
The problem with most (old) cars is you are trying to get over, is the large amont of small shitty cable, conections, switches and relays.
With this done, what a diffrens it made and I still used the old bulbs.
This may need a auto electrition to fit unless you confident.
I think I will do all I can on my s12, New head lamps, better bulbs (correct watt) and larger wirering, but not to big as the risistans will also go up.
Can any electical dude confurm this???
Or by a Million candel power torch and stick it to the bonnet.