The Rega tonearms(except the 250) are all iterations of the same design that started with the RB300.
Most people feel that the RB250 is the way to go, and do mods to it, because it doesn't have the spring like the 300 and others.
The 300 is also nice when modded, as are the others. However, the general consensus is that the 250 sounds better than all of them when modded.
The Origin Live Silver is generally thought to be better than any of the Rega arms(modded or unmodded), and is only about $900. For this reason, spending more than that for a Rega arm or modded Rega arm, seems unproductive. It is in a Rega base, but uses a proprietary arm which looks very similar to a Rega arm, but with some important differences. It fits into a Rega arm hole, and has the same geometry, so it is a "drop-in" fit for any table previously fitted with a Rega tonearm.
However, as the original thread poster was asking about low-mid mass tonearms, none of the Rega or OL arms would qualify for that, because they are all around 11-12 grams effective mass. But they will work fine with the Clearaudio cartridge that he mentioned.
