According to the website the Phonomena has adjustable loading from 30 ohms - 100 k-ohms in 128 steps. Seems pretty flexible. Dynavector recommends a load of >30 ohms on the cartridge. Typically you should load the cartridge where it sounds best to your ears. As you lower the load (meaning you are actually going up from 30 ohms), the more the higher frequencies will be accentuated. As you go raise the load the lower frequencies will be accentuated.
Here is an exercise you can try. You can take the value for the carridge impedance, which in your case if 6 ohms, multiply that number by 25, then take plus or minus 50%. In this case 25 x 6 = 150 ohms, plus 50% = 225 ohms and minus 50% = 75 ohms. So a load range for this cartridge is 75 ohms to 225 ohms. You may want to start there and see how things sound.
I have the 20XL which is 5 ohms so my range would equate to about 65 ohms to 185 ohms. However, I like the sound at 300 ohms. Have some fun with it and see what happens.