Looking for a suggestion for a good Phono Stage

Which Grado are you talking about and what are the specs, like out put and impedance? How much do you want to spend? What are you looking for from this Phono stage the ARC doesn't give you? I am sure if you specify these things the analog guys will help you.

That budget kind of limits things, I can't think of anything other than a Bellari with it's single tube, sorry.

I think your Mag input is intended for an MM cart., so if you are running it striaght in, without a separate phono stage, that is correct. If not, you may be phono amplifying your phono stage, which should amount to an unacceptable amt. of gain and is thus noisy. The Head Amp input would make sense as an MC circuit, but I am not certain about it. Can you download an SP-4 user manual?

Yes PBN that may be your "job"... as such, you are a professional who stands to gain from a suggestion involving a product you sell. Such a suggestion must be a biased, even if a good one. Having a motive without saying "dealer disclaimer" or the like, is really not the right thing to do. In the future you can free yourself simply by saying you are a dealer or manufacturer, that is simply more open and honest.