Steel is Good for a road bike. Current fabrications of steel are quite light.
The difference in weight between a good steel frame and aluminum,carbon or titanium is of significance only to more "hard core" bikers, etc. Losing 2 pounds of body fat will gain you more.
Don't go by brand, go by what frame fits you best. Most road bikes are going to be of high enough quality that what you might want to look at are the components, not the brand of bike. Bikes are sold in two separate parts - the frame and the components, which are standard between bike brands.
Specialized, Bianchi, Lemond, Trek, Cannondale, etc., are all top quality, but will feature the same components, i.e., either Shimano: Sora or Tiagra or 105 or Ultegra or Dura Ace or similar Campagnola components.
Some claim steel will give you a better ride, but frame geometry is the single most important factor in ride, along with tires.
Some will recomment a recumbent if you have a bad back. Depends on the back problem, however. Bents are used by a lot of folks, and most bent riders love them.
Get thee to a good Local Bike Shop and start trying out bikes. Have them spec you out for what type of bikes will fit you best.
You should think about Shimano 105 (or comparable Campy) as your bottom rung of component quality. 105 will do just great.
FIT is the most important thing. Certain frames fit certain body build better. I.e., Lemond's frame fits folks like me with a long body and short legs better than some other manufactured frames.
Last edited by DnvrFox; 09-23-04 at 06:50 AM.