You didn't mention if this is an e30 or e36...US or Euro spec...so I'll chime in what I know about e30's:
The US spec H4 ellipsoids are pretty good, optional on late model e30's. Mostly plug and play. The ultimate are the Euro H4 projectors, called 'smilies'. The downside is that they're all pretty expensive, maybe $350 or so. You have to get the whole mounting plate & wiring harness too.
The alternative is 'E-Code' Euro lighting. I have a set of H4 Hellas, Cibie and Bosch make great sets too. Very nice lighting, and they fit directly in the stock buckets as well. A new set of Cibie CSRs might put you back about $250 or so.
The cheapest alternative is the cheap EBay vendor that sells an adequate Indian version of the Euro headlights. Brand name is Autopal. He's about $80 for a set of H4/H1 replacements that are still vastly superior to the stock sealed beams.
They're all H4 low beams though, so if you're planning on HID upgrades you'll need to get rebased bulbs or adapter sockets. Typical xenon HIDs are much longer bulbs than the halogen H4s...the 'hot spot' is too deep and makes for really bad glare problems for other drivers. If I had my way (and unlimited cash), I'd have custom enclosures made that used newer BMW bi-xenon projectors and halogen high-beams. Basically it'd be e46 lighting for an e30.