Some of the DigiTech X series pedals have stereo outs. Stereo phase is pretty cool in my opinion.

To take real advantage of stereo, rack multi-effects have much better stereo effects options, including some traditionally mono effects that you can use in stereo.

The EHX Stereo Polychorus does an ok Leslie type sim, and it's stereo.

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R. Mutt

Guitar -> Wah -> Amp -> Cab