Mhu - choosing the right powercord is usually a matter of finding something which best suits your system - without going over the top. The Supratek will introduce some new benefits into your system and perhaps create deficiencies as well (I hope not). The cord which works best for you will ultimately be a matter of identifying what is introduced vs. what was taken away - and compensating.
Simple right?
In my system, Elrod PC's when used on amps and preamps are a bit over the top for bass but the EPS 2 Sig can create an awesome dimensionality when used on a digital source component.
For the Supratek, I usually find a more neutral power cord to work best. The two I like are the Electraglide Mini Khan (not the plus! the plus sucks!!) and the Moray James PWR 1.5. Moray's "new" PWR 2.5 can be good but I've heard mixed results with people who've tried the cable on Supratek's. Some like it and others do not whereas the 1.5 was almost unanimous - everyone I knew who tried it, loved it.
The one caveat is that if you are used to a more flavorful PC on your preamp (Shunyata, BMI Shark, Acoustic Zen, etc) you will not like the Moray James or Electraglide regardless because these cables are neutral and hence do not change the tonal balance of a component or create a hazy-sugar-sweetness to the music.
Since you've been using an Elrod on a previous preamp, I suspect your system requires something more neutral - (the EPS2 Sig is a bit less neutral than the EPS 3 Sig but still much more neutral than some of the other flavored PC's I've mentioned.)
Of course you'll want to give the Elrod a try but I think you'll find that the Supratek's bass (with the right tubes) is sufficiently accurate to the source and the Elrod may not be necessary in this application.
In which case try an Electraglide Mini Khan (copper) which will benefit the Supratek with increased transparency. Not transparency in terms of added highs - but more of a clean, purity to the sound. Much like live music vs. processed and compressed recorded sound. Or.. try the Moray James PWR 2.5 (the PWR1.5 is no longer available) for subtle improvement that introduces a lively & emotionally fulfilling sound & pace that once you've heard is difficult to live without.