“...does anyone have experience with a preamp that produces a big soundstage?”
I think most preamps in the $5K USD price range, especially if used, will throw a reasonably believable soundstage. Based on my experience having had a few different preamps, tube or SS, in my system, the difference is mostly in “how” the soundstage is rendered between the speakers. Some preamps have a more forward presentation with the vocals more into the room vs. others that are more recessed. And some have a wide stage but very flat. Your best bet is to try a couple, both tube and SS and see which has the sound quality you like when paired with your amplifier and speakers. If going the tube route, check the output impedance specs to make sure it mates well with your amplifier.
I think most preamps in the $5K USD price range, especially if used, will throw a reasonably believable soundstage. Based on my experience having had a few different preamps, tube or SS, in my system, the difference is mostly in “how” the soundstage is rendered between the speakers. Some preamps have a more forward presentation with the vocals more into the room vs. others that are more recessed. And some have a wide stage but very flat. Your best bet is to try a couple, both tube and SS and see which has the sound quality you like when paired with your amplifier and speakers. If going the tube route, check the output impedance specs to make sure it mates well with your amplifier.