My concern about doing an upgrade to the square or rectangular Euro
headlights is the cost of replacing one of the lights if it breaks.

The SA grill seems like it may be more cost-effective in the long run, if
you think you may break one or more lenses. Although this option may be
more expensive inititially, my understanding is that it uses standard-sized
lights -- so that you can replace them at a relatively low cost.

Vanagain has (or had?) the SA grill with the inner lights for $295:

http://www.vanagain.com/Accessories.htm#SA%20Quad%20Light%20Grille

After buying the grill and inners, you could add the outers for about $50
or so apiece:

http://lighting.mbz.org/products/products.html

I believe you'd need to get some pre-1985 headlamp buckets for the outers,
though -- another $20 or so at the boneyard?

In either case, the relay upgrade seems like the best place to start. This
alone may give you the brightness you seek.

- Kevin