Where do I find USB controlled digital potentiometers sampling a wide array of values?
If precise control of resistance is your goal, then digital pots are not a great solution.  Their resistance varies quite a bit, initially and over temperature.

Usually potentiometers are used in a ratiometric way, where the exact pot resistance is not an issue.

The device you linked uses the MCP42xxx digital pots, which only come in 10K, 50K, 100K. (datasheet)  Notice the initial resistance tolerance is ±30% and the typical drift is 0.8%/°C.  Also notice the high wiper resistance, which is why digital pots at low resistances don't make much sense.

Can you explain what you are trying to do with all these potentiometers?  You may find a different approach to accomplish your goals.