Welcome Sunkitten! I'm sorry you had to find yourself here but this is certainly a great place to be, under the circumstances.
I've had RLS since I was 19. Wan't diagnosed until 3 years ago, or so. I was prescribed Klonopin for anxiety. The first night I took it, I was amazed at the effect it had on my legs. It was wonderful. I continued taking it, with good results, until recently. Yes, I had to up the dose over time. I was taking 2-3 mgs at night. Started out with .5. That's the bad thing about Klonopin. Your body adjusts to it and it becomes ineffective. However, that's how it is with many drugs. I'm not surprised that.5 mgs isn't helping you anymore. It's the lowest dose. Your Dr. should know this and should be upping your dose accordingly. If, after adjusting your dose, you get good results again, you can take drug holidays. Which means, you could ever so often, switch to a similar drug and let your body reset. Allowing the Klonopin to work effectively again.
Most Dr.'s are hesitant, when it comes to Klonopin, because of the possibilty of dependence. Hopefully, your Dr. is one who knows that the chance of addiction is slim, when used appropriately. I'm not so lucky. My new Dr. was determined to get me off of the Klonopin. Which was ok because she was willing to work with me until we found another drug combo that is working. Right now, I am taking Mirapex (which 80% of RLS patients find effective) and Ristoril. I started with the Mirapex. It did a great job calming the legs but I still couldn't sleep. I started taking the Ristoril 3 nights ago and am happy to report that I've had 3 nights of good sleep.
Could you possibly switch to an anti-depressant that does not exhaserbate the RLS? There are a few. Like Wellbutrin or Remeron. Here is a link that describes the many medications used for RLS and there effects. You'll notice that most anti-depressants DO make RLS worse...as you already know.
http://www.rlshelp.org/rlsrx.htm
Here is a link to the RLS algorithm, which is a very easy to read tool for you and your doctor.
http://www.mayo.edu/proceedings/2004/jul/7907crc.pdf
From what I understand, the experts recommend that for those of us with refractive/severe RLS it is best to take dopaminergic drugs. That's what Mirapex is. It's an anti-parkinson's medication. Jumpyowl is much more learned about all of the drugs so maybe he'll have advice that's more helpful.
You're doing the best thing that you can possibly do for yourself. And that is to get informed! Read, read and read some more. Train yourself to be your best educated advocate because the medical community is very uneducated about RLS. Keep us updated. Again welcome.