I wouldn’t decide against [name_u]Finn[/name_u] just because of its popularity. According to social security baby names, [name_u]Finn[/name_u] ranks at 250 for the year 2013. That’s really not too bad; not even top 100. If that’s the name you love, then go for it. I don’t think it will ever be so popular where there’s gonna be like 5 Finns in one class. If you still aren’t sure about [name_u]Finn[/name_u], then what about [name_u]Flynn[/name_u]? Or you could use a longer version of [name_u]Finn[/name_u] to use the nickname [name_u]Finn[/name_u]. Maybe [name_m]Finnegan[/name_m]?
If [name_u]Evan[/name_u] is too close to your favorite girls name and you plan on having more kids, I would hold off on using it. If your next child is a girl, then you won’t have to sacrifice your favorite girl name because you had already used [name_u]Evan[/name_u]
I love [name_u]Finn[/name_u]. It’s my favorite boy’s name, and I’m pretty sure I would use it no matter how popular it becomes.
As for [name_u]Evan[/name_u], it’s currently ranked #55 in the U.S., so it’s possibly more common than [name_u]Finn[/name_u] in your area, if you live in the states. If it’s your favorite boy’s name, I don’t think you’d be sacrificing anything by using it instead of saving a similar name for a future daughter. There’s no guarantee you’ll even have a daughter, and you still get to use a favorite name for your son.