After a slow start, ADSL users now have a good selection of 802.11n hardware to choose from. But when it comes dual band routers, the selection is pretty thin. This Netgear is a prime example - it's the only concurrent dual-band ADSL router on the market.
http://www.pcpro.co.uk/reviews/wifi-routers/356587/netgear-dgnd3300
Not the best review of its wireless performance.After reading that and their recommendation you'd be better off with a separate wireless access point (i.e g router in bridged mode) for the slower devices and a single band N adsl router. I can't find similar performance specs for the Apple extreme base station (needs additional modem i.e Draytek vigor 120)
Must admit I have that router and do not suffer with it, the Mac operates on the 5GHz spectrum and the iPhone and PS3 on 2.4ghz, I have no issues with HD over wireless and speeds, a lot I guess depends on placement and equipment used and routers do not always behave the same across the board even if they are the same, also the router is only on its initial firmware, but it is rock solid.