Starsailer... I have several lights on my roof and they are properly aimed so I've enver had a problem with reflection or anything (though I wouldn't recommend it if you've got a sunroof!) I've got forward facing, sideways facing, and rear facing, so I don't worry about not having enough light

. I love driving around with the roof lights on, it's an awesome sight and I can't even begin to describe it... watching the beams of light as they stretch down the road for a long long ways

. I used to get a kick out of when I was housesitting for one of my co-workers (this was when I was first installing the lights) and this neighborhood had those street lights that are light sensitive, meaning if its dark they come on, if its light they don't. I could turn off the street lamps from about 1/4 mile away, LOL.
By the way, the best way to wire them is the way the manufacturor recommends. If you mount them on the roof you will need to extend your wires, but it still should be wired up exactly as recommended.
The altenator depends on your size of altenator, and honestly I don't remember how to check. If you have a 130-amp, no sweat, I've got 14 lights and my altenator can handle it just fine (for a short amount of time anyway, I've never driven with all them on for any extended amount of time), the optima as a backup is good. Working on a dual-battery setup.