Well its a case of how long will the router be useful.
ADSL2+ is about as good as it gets on the ADSL side of things. There are various options to ADSL2+ which Netgear don't support - Annex M is one which allows increased upstream speeds. It is unlikely to be of interest unless you are on Be (its an ISP).
On the wireless side of things I wouldn't bother buying anything which wasn't capable of 802.11n. The difference in real world terms is basically this :
802.11g (with WPA encryption) = maximum of 20Mbps for the whole wireless network
802.11n (with WPA encryption) = maximum of 50Mbps for the whole wireless network (with a following wind

- 40Mbps is sustainable though)
I am the only person who uses wireless in this house and 802.11n is MUCH faster than 802.11g
How long do you want it to last for? If its more than 2 years then get the DG834N.