For the bike you have, you should be able to get a Sanyo H27 hub and a wheel built around it for $100, maybe 125. A light would be about 60-75 for a decent one, so you're looking at $200, AT LEAST. There's someone on eBay selling a road wheel made with the Sanyo hub for $95, but you need a mountain bike wheel to fit. They don't have any at the moment but said they would in the coming months when I asked. The road wheel looked decent enough, so if they had an MTB wheel that's what I'd get.

All generators produce 6v/3a due to the German StVZO legal standard. They have the largest share of the generator light market so the rules they make are followed by all the manufacturers in all countries. It doesn't make sense to me that there aren't any that pump out more volts or amps for those of us not subject to German law. More watts output means more pedaling input, so you don't want to go too crazy there. All generator lights also work on 6v/2.4a in front and .6a in back, hence the 3a rating.

With LED lighting getting more efficient by the day, you should be able to pump out a lot of light with that kind of power, but StVZO comes into play again. These laws state that lights MUST be limited in their aim and throw, just like a car light. Not all light adhere to this standard. You can also wire up your own if you are handy with electronics. Most lights have a "standlight", where the light stays on for 4 minutes (StVZO) or more (or less if it doesn't adhere to the standard) when you stop moving.

You probably don't want a "bottle" generator, these are a lot less efficient.

All that said, you can buy a rechargeable battery powered front light that will throw as much light off, or more, for $35, with batteries, mount, charger, and a headmount included. Rear lights are still catching up to the fronts in efficiency, but they aren't expensive.

I haven't tried dynamo lighting yet myself, mostly because I'm still enamored of my battery lights. It's a lot less hassle, plus I can't see putting a dynamo on my road bike. I could see it on my MTB, but it would cost more than the $150 I paid for the bike.