Phono Stages with External Power Supplies...Worth It?

@lewm incorrect. Merely asking for thoughts on external power supplies in a general sense

I'd suggest buy it sans PS and see how you like it. The real question is, will you always wonder? 

In my years of dealing with Naim equipment, I found that adding a power supply made a huge improvement in the sound.  Not just "smoother" or "more musical" or stuff like that.  It made the music sound more musically complete, like going from standard TV to hi-res.  That may not be the case with your particular piece, but you should absolutely try one with a return privilege.  I was talking about power supplies with Peter Qvortrup from Audio Note and he told me that many people have severe space limitations, dictating 1-box solutions, but otherwise, he always prefers a separate large PS.  Enjoy. 

fsonicsmith, I am surprised you would place the AR Ref6 above the Steelhead, but if you are a "solder slinger", like me, I can suggest some very small changes to the Steelhead that make it sound worlds better. Either PM me or indicate here if you want the information and my suggestions.

Lewm; I don't. They are two separate categories. The Steelhead is a phono stage and the ARC Red 6 is a preamp. I used them as examples only. At the outset of my post, I mentioned that preamps and phono stages are very similar and they are. They both take a low voltage signal and apply attenuation to them. They are both very susceptible to EFI/MFI from transformers. Further, I love my Steelhead and if Mike Fremer is correct that it is no longer reference quality, I don't care. I would never mod it. The folks at Manley are incredible with their product support and I would never jeopardize my warranty and their support with mods. 

Has anyone suggested listening and deciding for yourself whether it is worth it? ;)
This more than anything else will tell you.

Any dealer worth his salt will be happy to swap them out for you at the dealership or lend you both for lengthy home demo. Either way you will know for sure rather than acting on random opinion?