Okay as the official named after Jane Austen mumsnetter I think I have a right to comment here!
Darcy is a surname. Darcy for a girl I think is really quite cute, despite it becoming rather 'popular' lately. My fictional dd3 has Darcy for a middle name.
Darcy for a boy I'm not quite convinced by. If you want a name for Austen conotations you could consider -
Edmund (love it) As the great lady herself has Elinor say @the name Edmund. It is a name of heroism and renown -- of kings, princes, and knights; and seems to breathe the spirit of chivalry and warm affections";
Edward (maybe a bit too 'solid' sounding and it sounds like you want something a bit edgier: I may be making huge assumptions here so apologies if so);
Fitzwilliam - could be Fitz or William as the whole is a bit much imho;
Henry;
George;
Frank!;
Frederick.