If you like the feel of the RFs you have, you might be a little disappointed in the HHKB. The layout is tremendous, though, and once you get used to it, it's really hard to go back. Personally, if you have two RFs, I would skip the HHKB unless you are really in need of a portable keyboard.
@isp
If you pull the spacebar cap, there is a large spring in the middle where the switch is. If you take out the spring, the spacebar will be a lot lighter. It won't be as solid-feeling, but it will work just fine.