I stock more than one tanning brand Chris, one being Sienna. To be honest, the Sienna is the least requested now.
I do think there are other solutions that suit different skin tones better. IMO Sienna isn't as good on the cooler skin tones, and it does really require maintaining properly for an even fade....which yes, I know we should with all brands, but there are others that fade better with no maintenance (trut me...I've been far tooo busy to 'maintain' my own may times - so I know!)
My suggestions for an alternative that complements Sienna would be....
Celebrity Secrets - the React range. IMO the very best all round solution I have ever come across, and I've used/tested plenty!
Vani-T (this range also has the express solution so has differentiation there.
Tantrick Essence of Summer - practically no colour guide, so fantastic for brides (no rub off on a wedding dress if they don't exfoliate first or shower off as well as they should)
And I've just tried the Nouvatan 10% - a sample I was sent a while back and I have to say, I'm vereeeeee impressed so far!