Well, just so you know, even if you could enable N on your Mini, you wouldn't actually experience faster Internet speeds since there are very few, if any, ISPs that offer speeds greater than 54Mbps (that's the speed of a G connection).
There are only two real benefits to 802.11n: network speed and range. If you have several N machines on your network, the transfer speeds between them will noticeably improve with an 802.11n router. The increased range isn't just for N products, but for B/G products as well. So if your Mini was far away from the router, getting an 802.11n router could help if you were getting slow speeds and/or a poor connection. But since that doesn't seem to be a problem for you, you wouldn't really see any benefit with 802.11n, at least not for the Mini (not sure if you have any other Macs).