I love [name_m]Benjamin[/name_m]! From your list I like [name_m]Oliver[/name_m]. Some other ideas:
[name_m]Simon[/name_m]
[name_m]Alexander[/name_m]
[name_m]Joshua[/name_m]
[name_m]Louis[/name_m]
You’ve likely already decided at this point, but I think [name_m]Benjamin[/name_m] and [name_m]Gabriel[/name_m] would be a stunning pair. I have a [name_m]Gabriel[/name_m] and we are kicking around [name_m]Benjamin[/name_m] for a potential little brother in the future. I also love [name_m]Benjamin[/name_m] with [name_m]Oliver[/name_m], [name_m]Simon[/name_m], and [name_u]Elliot[/name_u].
[name_m]Gabriel[/name_m] goes very well with [name_m]Benjamin[/name_m] as does [name_m]Oliver[/name_m]. [name_m]Oliver[/name_m] however, is not my taste.
Other names you may wish to consider…
[name_m]Edwin[/name_m]
[name_m]Lucas[/name_m]
[name_m]David[/name_m]
[name_m]Sebastian[/name_m]
[name_m]Maximilian[/name_m]
[name_m]Isaac[/name_m]
[name_m]Josiah[/name_m]
[name_m]Joseph[/name_m]
[name_m]Harrison[/name_m]