The slick feeling you don't like is the way your skin feels when soft water lets your pores open. Hard water clogs your pores and prevents the nayrual oils of your skin to flow.
Many people who start out not liking the slick feeling and get used to it after a few weeks and never think about it until they visit someone who has hard water and then they miss home.
As far as your orchids, I don't know the water requirements but you have a couple options to avoid sodium.
One is to use potassium chloride (KCl) in your softener's brine tank. Info on KCl here...
http://www.softeningsalt.com/index.html
Another option is to plumb so that your entire house gets soft water but the garden gets hard water. This may be the best solution.
In order to correctly size the softener your daily water use and the garden might impact that number in a BIG way.
As far as shopping for a softener here's what I recommend...
The water specs you linked to are what is certified at the treatment plant not necessarily what is coming out of your faucets.
First, get a complete water test from an independent lab. This is a MUST DO because without it everything is a guess. A quickie water test from Sears or a water softener company won't be complete. They only test for the "profitable" stuff.
Second, hit the Yellow Pages and call at least three local water treatment pros. Make sure you call at least one of the big dogs like Kinetico or Culligan and at least a couple independent pros. DON'T TELL THEM YOU HAD YOUR WATER TESTED.
Give each an opportunity to offer suggestions and provide you with a quote to meet your water treatment needs. IGNORE ANY THAT DON'T TEST YOUR WATER THEMSELVES as they can't speak intelligently to water treatment without knowing what needs to be treated.
Ask lots of questions. Softeneing the entire house or just the water heater (bad idea)? Warranty, parts & labor or just parts, how long and on exactly what? Install, permits required, licensed plumber? Routine maintenance and costs? Do they stock parts? Response time for emergency (water leak) calls? If they don't explain things to your satisfaction that is a good indicator of how you'll be treated after the sale.
After they've gone use your water test to compare with their's. Are all your treatment needs being addressed?
Ask your neighbors if they have any water treatment experience. They might tell you who's good or who to avoid.
Come back here and post the specific recommendations and hardware with the costs and we'll give you our opinions.