ARC SP16 vs SP8

What's the rest of your system? Just about any piece in an audio system can mess up imaging. I've never cared for the SP-16, myself, but I wouldn't necessarily say that its the cause of your problem.

As far as your analog setup goes, I don't think thats your problem. Even with modest equipment, records image very well. When people either get back into analog or try it new, for the 1st time, their first remark is almost on always how good the imaging is.

Nick, you make a great point, i might have my speakers too close to eachother. I will try to space them further apart. My room is small which is why i bought magnepan mc1 on stands with a sub for the low end. They are about 4 feet from the wall. Im gonna space them out about 5 1/2 to 6 feet apart. I had them about 4 feet apart. I usually sit 6 feet away from the speakers. The sub is behind the right maggie in the corner which sounds really good.
Elizabeth, 1,400 for a 15 is steal if its anything like the 10 or 11. I paid more for the 16 lol. If i ever see that pre amp for that price im all over it. I also use a ps audio duet which at first was really bright but calmed down over time. Im not sure if it improved my system, but i havent removed it.

Oh yea as far as cables are, i use tara labs prime m2 from the turntable to the preamp, tara air 2 from the preamp to amp, audioquest rocket 88 speaker cables, and shunyata venom power cords.

I've found the imaging of the SP16 to be quite precise and capable of a very wide soundstage. I'm at a loss as to why you would find it "too mono".

Just read your followup - sounds like speaker positioning may be your issue. Might be difficult to achieve a wide soundstage under those circumstances. Speaker positioning and proximity to walls etc will have a greater effect on imaging than (competently designed) electronics.