I'll find out soon enough.
The real answer is that it depends on whether or not your source is going to have issues driving a low impedance load. I used a 10k pot on my first beta and had no issues with a variety of sources. Also, from what I'm told the only sources that are likely to have issues with low input-impedance amps are tube output sources. And even then if the tube output has a buffer on it (some do, some don't) it should be fine.
Still not sure what I'm going to use for pots on my balanced beta since I've moved to 4 channel vs. 6. Also, for gain I'll be going either 2/4 or 3/6. If the K340s don't have enough balls with the 6 via balanced drive then so be it. I'm not re-configuring my whole rig for them, my name ain't Jay.