Cartridge loading


I have a Benz Micro Gullwing low output cartridge and supposedly has a load rating of >400 ohms. I am using an Einstein Turntable's Choice phono section which had 69db of gain and has four sets of interchangeable plugs to vary the load. The problem is, the highest load available is only 300.

When I checked with Einstein they said there is a 500 ohm "load" when using NO plug. They don't make any custom plugs so I am stuck with one of the four sets of plugs that come with the preamp. What does that mean sonically or electrically? What changes could one expect if a 400 or even 1000 ohm load could be applied? Is there an inherent problem with using no plug in the SE slot?

Thanks in advance.
wynnosu
Atmasphere brought up a reason for having some loading with stages sensitive to RFI. I helped set up a table for someone with a Hovland preamp. We had problems with noise that turned out to be RFI. The factory "default" loading for the Hovland turned out to be 100k (essentially no loading). The unit had to be opened up to find this out and to make a change. Adding some loading cured the RFI problem.

A cartridge manufacturer, I believe Jonathan Carr of Lyra, mentioned another possible reason that loading might help. He noted that the response peak of modern cartridges are so high in frequency that loading should have minimal effect on audible frequency response. However, he speculated that some phonostages or linestages might be incapable of handling the signal level of the ultrasonic peak of cartridges, in which case, some loading might help in taming such peaks.
Oh horror! I use a 'blanco' record (without groove) for the
bias adjustment. Not to determine the bias force but to have any idea where to start. The same apply for the 10 x 'rule' . One needs some orientation 'point(s)' and can 'tune by ear' from there. Or so I thought.
Larryi, Jonathan Carr and I are talking about the same thing.

The 'ultrasonic' frequency can be in the MHz. Sometimes its easier to think of that as RF which is why I put it that way.