Just another reminder about the grounds, as Alan mentioned above.
You won't see much of a difference unless you use heavy gauge wire for both the hot AND ground wires. As Alan said, this means running dedicated grounds from the lights back to the battery.
My first upgrade was from halogen sealed beams to the (cheap) EMPI H4 conversions (the sealed beam headlight is replaced by a reflector housing shaped like the old headlight that contains an H4 bulb). This made a substantial difference.
Then, I replaced the stock wiring in my VS with short runs of dedicated 12-gauge wire for both hot and ground (controlled by relays). That made another substantial difference. The lights are now about as bright as standard lighting in a basic, modern car (Toyota or Honda without any lighting upgrades).
You should be seeing that level of light out of a basic H4 conversion, properly wired. If not, you may have other problems, like corroded connections at the battery (either hot or ground - or both). Or, there may be some corrosion in the the three-pronged connectors at the headlights.
These can be hard to spot. They may feel solid, mechanically, but be corroded internally. Pull the wires off the battery, sand down to bare metal, and reconnect.
Or, of course, the battery may just be tired. Any Autozone will do a free battery and charging system check for you.
Another thought is that if you're using a basic H4 conversion, the bulbs might be really cheap and substandard (like the bulbs that came in my EMPI units). Try swapping the bulbs with name brand (i.e. Sylvania) bulbs rated for at least 55/60W (55 watts low beam, 60 watts high beam).
Good luck!