I never worked on UC560 and SA-520 but I guess theuy must support 'Nat' and general routing (atleast static). Based your diagram it will work if you place DATA and Voice on 2 seperate subnets and not looking to have any commnucation between. One thing.. when the traffic hit the internet both share the same link. So you may need some QOS at internet edge and may want to consider L3 switch.
Hth
MS
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