Extension cord advice

Here are the only advantages over an extension cord.

6 outlets that are circuit breaker protected and EMI/RFI noise attenuation.

DeKay

I am not super concerned about surge protection -- is there much benefit to noise attenuation given that I'm not using a true conditioner?

It all depends on if you can hear it or not. Try plugging the turntable & phono preamp into an extension cord only and see if you can detect additional noise. Depending on the design & quality of your preamp, it might be dead quiet with either. If you don't hear a difference, you have your answer.