Charlibear - I would hate to know the extra cost to steel - I think it will be a ouchy cost. I think I read once steel framing is about 20% the cost of timber. Then you need to make sure things like noggins for dryers and TVs are done at the fab stage as unlike wood you can't really add it later. However with termite treated timber (which mine is), then a termite barrier plus follow the rules of no high garden beds along wall of house, don't leave timber etc against house or piles of mulch or soil plus have a yearly inspection and you should be fine. I have dealt with termites the last 9 years in my current house - PITA - but I have always caught them early enough to treat - most of the damage I have repaired was previous attacks that had been treated and then I found the damage when renovating and tearing down walls.
I'm having excess drainage for my front also as my driveway slopes down alot, they also raised my flooring for my garage to stop it being so slopy and give them a chance to slope away from the house at the front. I have 2 drains on both sides of the driveway just to take the drainage for the driveway. It was part of my quote when they had the plans etc and knew they needed to do it - so I don't know the extra cost as it was part of my base price.
Townsville - $500 for one CSD - wow, I think mine were $280. I put it in so they can have some privacy when friends come over and keep the noise in with video games etc while we are in the other living areas. We also put in soundproofing between bedrooms 3 and 4, it was about $400 for one 3m wall.