While Quilter amps are designed to run 4 ohm and 8 ohm cabs/loads, you can run a 16 ohm cab with your amp. But there are a few things to note:
A 16 ohm load will cause the output of the amp to behave a bit differently. The power of the amp will nearly double when being ran, so you will have to accommodate this. To make this work, you'll have to keep at your master at or below half the wattage of your cabinet that you're using, at maximum. This way, the amp will be able to handle voltage swings and you do not blow out your speakers.
For example, if you are using a Tone Block 202 with a 200 watt cab that is 16 ohms, you will have to keep your master at or below 100.
If you plan on running a 16 ohm cab with your Quilter amp, just plug it into the 8 ohm jack on the back of the amp.
However, running two 16 ohm cabs will not be an issue. Running two 16 ohm cabs will result in an 8 ohm load and will cause the amp to behave normally. If you wish to do this, just plug one cab into each speaker jack and you're good to go.
NOTE: This does not apply to the discontinued Bass Block 800/802. Running a 16 ohm cab with the Bass Block will decrease the wattage to 250 watts.