ARC SP16 vs SP8

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.

Yea im starting to think that even 6 feet apart is still not enough, im gonna have to live with it. Im not sure how far i should sit from the speakers.

Good imaging usually starts with a set up of a triangle. Seat perhaps 10 to 15 percent further away from the speakers than the speakers are apart from each other. An equalateral triangle is a great place to start. FWIW.

Honestly from what i heard about the 10, the cost to retube it is alot. What i do like about the 16 is how neutral it is, im not sure if i would like a warmer coloration. I think the 16 is more closer to the sound of your 15 than the 10, but mabey not as detailed or as front row.