I've owned the 630, RT, original Elan, and 1v. The original Elan is way, way quieter than the 1/1N/1v. It's also very cheap these days, if you can find one in decent condition. However, if you're used to the responsiveness of a 1-series camera, the Elan will take some getting used to.
The RT is a very interesting camera, and definitely not so obtrusive as a 1-series. I think the biggest drawback is that manual metering is primitive and awkward. And of course, if you're trying to follow things that are happening quickly, the AF isn't in the same league as later 1-series cameras.