in audio, what in the system gives us the soundstage ?        I ask this as when I had the system in the living room I had one system that was :

anthony gallo 3.1's
edge amp
Belles 21a preamp
Technics 1200 mk2 w / AT 150 cart
bellari preamp
Synergistic Research sp cables, various low end IC's

and that system had everything ....soundstage , separation, detail.....and was enjoyable to listen to.       got out of the hobby for a bit and when I got back into it, I went with this system :

Magnepan 2.6 qr's
w4s mono blocks ( 250 each )
Lector Zoe preamp
PS audio phono preamp
Technics 1200 mk 2 w/ AT 150
Morrow Audio sp cables and various low end IC's

sold that system and had the chance to move the next system from the living room which had the cathedral ceilings,into  what used to be the master bedroom.....and now have a room that is good size 17 w x 21 l  8 ft ceilings and went with this the first time :

Magnepan 3.6r
Krell amp
Audio Research Ref. 2 mk 2 preamp 
Sim audio lp 5.3 phono preamp
Acoustic Zen sp and IC's
VPI HW-18 MK 2 w/ Moerch arm / Ortofon 2m Black

the Magnepans were way to big for the room and didnt like the AR preamp as it just didnt sound good....sounded cold due to the 6h30 tubes ( others may like it, but I didnt ).......sold the speakers, amp and preamp  and  ic cables and went with 

Tyler Acoustic Halo 2 speaker
Maker Audio G-9
Belles Aria
Sim Audio 5.3 phono
vpi  hw 18 mk 2 w/ Moerch arm / Denon 103 cart
Acoustic Zen Satori sp cables, KCI silkwork IC

this system is very  clean sounding and you can listen to it for hours and never get tired of it......but I just dont have the soundstage like  I did when the system was in the living room.        Room is treated with panels, have moved speakers in / out  / up / back, etc....and same thing.....       

So is it the room that ( cant think of the word, ) controls the soundstage or is it the preamp, the turntable / cart ?

I've said it before and I'll say it again. By and large speakers are place too far apart. For best results one should start with the speakers fairly close together then gradually move them farther apart. I suspect you'll find the best soundstage occurs when the speakers are relatively close together, say 4 or 5 feet. Obviously some (big) rooms dictate that speakers be farther apart. 
Part of imaging is also frequency response, there are a number of tweaks / cheats in speaker design that can enhance this.

What I suggest is listen to your speakers from about 2-3' away. This will give you an idea of the very best performance, with little room interaction. If they don't image to your satisfaction then, they won't do better at normal distances.

Of course, room acoustics matter, but they can't make a speaker better than it is. Assuming ideal placement, I find that acoustics in the plane you want to improve is the best approach. If you want to improve height, add treatment on the floor and ceiling, etc. Don't ignore treatment around the listening area, especially diffusion.

I've gone through several systems, all in the same room, with the speakers set up relatively the same way using a formula from the Cardas website. A structured room with walls and a ceiling has helped me to retain a nice soundstage no matter what gear I use. Experimenting with speaker placement or moving all the gear to another part of the room is something I would try, or another room maybe. Another trick I learned long ago is to not block the front watt with gear, keep the gear low or even on the floor because the back part of a soundstage will terminate where it hits something. If you are a gear stacker, the speakers need to come out into the room more and the seating position needs to be moved back accordingly. Changing gear is fun when it works.
@addyson815 - As you have seen above lots of opinions and none of them are wrong - it’s more a case of a combination of all of them plus some others.

First the speakers play a huge role - when you auditioned them did they have a good sounstage? My speakers have always sounded transparent - even in the showroom.

The amount of Toe-in can have a significant effect e.g.
- The center line of Tannoy speakers should cross in front of the listening position
- My speakers are happy with about a 15 degree toe-in
- some like zero toe-in

Next - placement in the room - ideally the distance from the wall behind them should not be the same as the space each speaker is in from each side - it can get quite boomy otherwise - my current room is 16.5 x 24 with another 20 ft of open space behind the listening position - the speakers are 8 ft from the wall behind them and just over 4ft from each side wall, so there is around 8 ft between the speakers. NOTE: all measurements are made from the center of the tweeter - not the back or mid-point of the speaker

Then room treatments - I have played around a little with these in a couple of spaces - one 8 ft ceiling and another 12ft ceiling (and concrete) and found that the most effective treatments tend to be those around ceiling level - namely sound absorption on top of bookshelves and cabinets and vinyl blinds behind the listening position dropping approximately 15" from the ceiling. Broadloom on the floor works well, but if you have hardwood - try a large area rug.

If your room/system generates standing waves which can manifest as loud booming bass on certain low frequencies - leave any fixing to last - it may resolve itself with correct placement, but otherwise will require a more sophisticated bass trap

One thing I have found to provide the very best soundstage image details are my cables.

Some may argue that cables can be tackled once everything else is sorted but they play a key role in getting an exceptional sound stage. I've even found that image can be effected severely by connectors (i.e. RCA's and bananas and cables can effect the way each component works. 

Then there are dependencies e.g.
- speaker placement and toe-in are linked.
- speaker placement is dependent on furniture materials and location

I would start with as much distance behind the speakers as your furniture allow, then play with the distance from the side walls and toe-in. A couple of inches can make a difference, so move in small increments

Once position seems good - then try some room treatments and then try adjusting the speaker position and toe-in all over again - and again

You will get there - it just takes time

Regards - Steve

geoff and mj, I agree. But I would say about 6 feet between speakers in small to medium size room. I can't keep all the gear on the floor, though, not enough room in the room, I only keep the turntable close to the floor. Another trick, totally unscientific, you could try. Distance between speakers should be about one and a half height of a speaker. About. Speaking of the same room size. Might not work in all cases, sure.