How to change PlotLabel after plot?

Okey, so I have this code that took super long time to plot. It’s a density plot and let’s say that I would like to change to position of the BarLegend of the plot. I want to do this without having to redo the plot

As an example. Let’s say we have the plot

p1 = DensityPlot[Sin[x] Sin[y], {x, -6, 6}, {y, -2, 2},
  ImageSize -> {600, 200},
  AspectRatio -> Automatic,
  PlotLegends -> Placed[BarLegend[Automatic,
     LegendMarkerSize -> {550, 30}
     ], Above]
  ]

and I want the BarLegend below instead of above the plot. How can I do this after the plot?

I’ve tried various methods

p1 /. PlotLegends -> Placed[BarLegend[Automatic,
LegendMargins -> {{0, 20}, {-15, 0}},
LegendMarkerSize -> {500, 30}
], Below]

and

Show[p1, PlotLegends -> Placed[BarLegend[Automatic,
LegendMargins -> {{0, 20}, {-15, 0}},
LegendMarkerSize -> {500, 30}
], Below]]

Nothing works.

p1 /. Placed[a_, Above, b_] :> Placed[a, Below, b]

ReplacePart[p1, {-1, 2} -> Below]

p1 /. Above -> Below (* or *)
Block[{Above = Below}, p1]