How Do Amps Affect Soundstage?

There are numerous significant electrical and physical differences between a stereo amp and a pair of "identical circuitry" monoblocks. Here are four:

One electrical difference is crosstalk (L signal getting into R, and vice versa). Crosstalk is the result of inadvertent "leaking" of signal from one channel into the other. Two physically separate amplifiers are going to have less crosstalk if all other things are "equal".

Another difference is power supply loading. When electrical demands presented by output devices in one channel create fluctuations in available power, performance of the other channel will be degraded. Physically separate amplifiers have more electrical distance between their separate power supplies, and again, all other things being equal, the separate amps perform better.

High currents in the chassis of a two-channel amplifier will modulate the electrical grounding within the stereo amp. Disturbances to electrical ground are often discussed as problems in precise amplification. 

Even chassis vibration, propagating from one channel to another in a stereo amplifier, may cross-modulate signals and degrade performance. This is most often discussed with tubes -- microphonics. 

Amps are the heart of your system, the foundation from which soundstage is developed. A make it or break it kind of thing. An example of amazing soundstage can be heard in vintage quad amps like the 405-2. Among other qualities that may or may not be appealing to everyone, this trait is a product of the amplifier itself. 

I am not anaudiophile in knowledge, but have spent like one.

I have the ARC Ref 6 paired with a Bryston 4b cubed.

Recommended match.

I was finding I could not get the system to 'juice.

It was explained to me that the volume control on the 

Ref 6 is the limiting factor ( something to do with its design and gain ).

Piont is if you really want to ctabk the volume the amp

Is limited by the ref 6 pre.

On that note does anyone know if the volume control can be modified?

Mossy

Lots of noise above. An eight watt amp can produce an amazing soundstage. "Can" when the loudspeakers are carefully chosen and properly positioned in the room. It is not about power or monoblocs. It is simply a matter of good design and implementation.

Standing waves and room reflection have the most impact on soundstaging and imaging (often confused but different qualities), speaker choice and positioning second, selection of electronics third, and choice of cabling is likely last. Within that third category, "electronics" is source which is admittedly a bit sloppy when the source is vinyl but certainly the cartridge and phono stage are essential and electronic.

@Mossy, that business of the Ref 6 Pre having a badly designed volume control is pure garbage. You have ten posts (Yes, my profile only shows 80 some but I had to change from Fsonicsmith to Fsonicsmith1 due to password problems and have hundreds and hundreds of posts). What is your basis and where did that allegation come from? No need to answer. I don’t particularly care to know.

My apologies wrong thread.

Coffee might help