Try Sylvania SilverStar $25 each

or

Phillips Extravision $15 each

Both are a little higher wattage than regular 9004 and both do put out a brighter and deeper output. These bulbs won't burn your wire or harness either.
Go to either company website and have a look.

As Steve Ringlee noted in another post, the problem with going to higher wattage lamps in the headlight assemblies in your car is melting both the plastic electrical connectors and the plastic headlight reflector.

I recommend installing headlight relays which will deliver full alternator output voltage to the headlights. I have done this on three of our 700 series Volvos and I am very pleased with the improvement. Go to http://www.vclassics.com/archive/relays.htm. The article recommends using 10 gauge wire, but 12 gauge wire will give great results and is easier to install.

have you already tried cleaning the insides of your headlamp casings? if not, do it. they're plastic and turn yellow with age. make sure they are aimed properly as well.

cost: some time and $0, check the FAQ for procedure.

if afterwards you still don't have the desired brightness, try some expensive PIAA bulbs (www.piaa.com) that'll fit in your system. what i've seen of them looks good, but of course, comes at a price. ($75 a pair I think?)
--
Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'

If you are a police officer please ignore this...Tried and true method...BRIGHTER LIGHTS...

The auto parts supply company "Jegs" www.jegs.com has "off-road" use bulbs that are 80w/100w for about $35 for a pair. I tried to get some localy but the store wouldn't sell them to me. My Dad ran these in his 1990 740 and I LOVED them.