[name_u]Spencer[/name_u] [name_m]Hayes[/name_m] sounds very natural together. My other pick would be [name_u]Spencer[/name_u] [name_m]Grant[/name_m].
A few other ideas
[name_u]Spencer[/name_u] [name_u]Jude[/name_u]
[name_u]Spencer[/name_u] [name_m]Zane[/name_m]
[name_u]Spencer[/name_u] [name_u]Rhys[/name_u] / [name_u]Reid[/name_u]
[name_u]Spencer[/name_u] [name_m]Graham[/name_m]
I like the suggestion of [name_m]Graham[/name_m]. Or [name_u]Spencer[/name_u] [name_m]Bram[/name_m]…
[name_m]How[/name_m] about [name_u]Spencer[/name_u] [name_m]Piers[/name_m]? Popped into my head immediately.
[name_u]Spencer[/name_u] [name_m]Clive[/name_m]
[name_u]Spencer[/name_u] [name_m]Charles[/name_m]
[name_u]Spencer[/name_u] [name_u]Rhys[/name_u] (already mentioned, but I love it!)
[name_u]Spencer[/name_u] [name_u]Morgan[/name_u]