The best lighting is getting all the essential elements in place, and in the case of the US Volvo 850s you've almost been certainly dealt a mind-numbing weakness - US DOT lenses. The factors to consider are:
   ? light distribution (lens & reflector)
   ? light temperature (whiteness)
   ? light output (lumens)
   ? wattage

The most important thing to get on the car is a set of e-code lenses. These bend a much higher percentage of the light down to the pavement where you need it, and also provide a wider sweep of close-in lighting, and additional strength down the right hand side for road signs and curbside hazards. Volvo's US DOT lenses, on the other hand, are a pathetic implementation of a bad standard, a standard which distributes it's light as a fuzzy forward glow, at least half of which is above horizontal (and into the trees and sky). I bought the OEM (Hella) lenses, about $210/pair. Others here have paid less, and Punxsatawney Phil has found a third party maker for perhaps even less. You can order just the lenses, and changeout is only 10 minutes per side. (To confirm whether you have DOT or E-code, look at the lenses already on the car. E-codes will have E, E2, E4, etc in a cirtcle embossed right on the glass. DOT will have something like DOT, US DOT, ANSI, etc.)

Get the whitest light you can afford. In the case of the 850, the Sylvania SilverStar are a good choice. They produce 30% more light (lumens) and they are a couple hundred degrees K whiter. But they'll perform better behind e-codes because most of the additional light will make it to the roadway. Otherwise you'll lose about half of it directly into the retinas of oncoming drivers. Here are a few things to note about color temperature: 5000 degrees K is neutral daylight white. Any light rated above will appear bluish to oncoming drivers, and below that rating the light is more yellow. The SilverStar will get you 4000K...excellent for a 9004 halogen with a plastic base. If you have the bucks, you can do an HID conversion to get Xenon arc-lighting. Aftermarket kits start at $400 - but you have to add the price of e-codes to that, as HIDs are not street legal without them....you'll blind oncoming drivers.

increased wattage isn't the answer. At least not befor e-codes. And if you DO go for the pumped wattage, get spare connector parts or build your own harness and connectors. Volvo's notoriously suspect electrical system is wired almost exactly to 55W tolerance. Overwatt lamps will melt connectors, and you risk warping the reflectors, too.

auxilliary lights. I always recommend to other drivers concerned about lighting they consider auxilliary lighting like foglights or driving lights. Foglights provide a lot of close-in illumination, a wide sweep of light for cornering, a hard cutoff that eliminates glare in bad weather, and a low mounting point which adds contrast to the road surface at night - easier to pick out road hazards. Volov OEM is good, the wiring harness is already in the car, and the kit will include everything you need to hook 'em up and turn 'em on. Driving lights come on with your high beams, and should be mandatory in all those RWD Volvos (and 93 850s) that run two-filament, single bulb systems. I'm evaluating them right now for my wife's 940, because the stock high beams just don't get it done.

There. Probably more than you wanted to know.
--


David
1998 S70 T5SE // misc mods (mostly lighting) // red calipers
1992 940 GLE // Hella Micro DE foglights and 170K