An amplifier has little affect on soundstage.

Most of it is the speakers themselves, and their placement.

Small changes in placement can make a very large difference, so experiment.

My past experience is that you are not going to get what you want in any cheap amplifier from Parasound or Adcom.

You might get lucky and find a NAD or Rotel that would be decent. What you need, to get much inprovement, is an amplifier with a very low output impedance, which in practice means a power output of 100 watts per channel or more at 4 ohms.

That is a pretty low price range.

What is the center-to-center distance of your speakers, and how far is your head from the speakers when listening.

One thing that can make a TON of difference in imaging is the amount of toe-in. I had my speakers toed in so they were pointing at me, and the imaging was not very good. The imaging is MUCH MUCH better with mine when they are not toed in at all.