I think either router including the DGL-4500 is good. However somethings to consider:
What are your wireless needs? Have any client side HW that supports 450Mb and higher connections yet?
Are you needing IPv6 yet?
Ya, it's nice to future proof if you want to and get something faster now. You can update older HW that doesn't support higher Wifi connections to a point:
Bridge Mode vs Relay vs Acess Point (AP) / Routers vs Dedicated Acess Points (AP)Also things to consider is your ISP service and ISP modem support. It's highly recommended to use stand alone ISP modems with out any built in routers. However in some cases that can't be helped as mentioned in the above link.
I think both 8 series routers perform well. Some people claim the 827 does a bit better on performance and I can't verify this as I haven't experience one yet. I do enjoy my 857 and it does handle everything I throw at it. I recently streamed BD from my file server through it last week to my Boxee Box. No issues seen. I game on H4, MW and BO and don't see any major issues accept for the normal lag that comes from others or the gaming system servers maybe. I'm the only one at my house that games so I've used QoS both ON and OFF. Not much difference however it does help in households with multiple gaming consoles and use of the internet with other devices while gaming.
The DGL-4500 is still a great router however eventually some of the features that it doesn't carry will be needed at some point, depending. It can only do one or the other WiFi freqs unlike the 8 Series which can do both. And it doesn't have IPv6 and won't. Other than this, the 4500 is a solid router. I still have 3 of them and use one as an AP connected to my xbox. I know many people that still use them has there main host router or having them as APs or back up routers.

The use of CAT6 LAN cabling is highly recommended.
Let us know if you have any more questions.
Let us know what you go with.