Understand.
All 8 series routers are and do have the same features and performance of the 825. Dual banders. Newer generation routers do have a few more features than the 825 does like storage or cloud. However the antenna configuration is different on the newer 8 series, the Cylindrical looking routers:
http://forums.dlink.com/index.php?topic=51380.0I haven't opened my 826L to confirm if the antenna configuration is the same as the 645 however I presume it's very similar to the 645, just in a smaller case.
As you can see at towards the bottom of this linked page:
http://www.dlink.com/us/en/home-solutions/connect/routers/dir-826l-cloud-gigabit-router-n600It gives the differences between these model routers. Pay close attention to the row with WiFi Speed. This is the actual connection speeds between the router and devices that is possible. Not actual file xfer speeds, thats a different animal. So if you have supporting WiFi adapters, you should see WiFi connection speeds at 300Mb, UP and DOWN on 2.4 and 5Ghz. As you can see, the other higher model routers can do a faster connection with devices, however, please understand that your devices need to support the faster connections, so newer devices can or some don't. Please check with the Mfr of the devices to see what they can officially support. Also some devices can be updated or connected in a way that you can use the faster connections speeds by using upgraded devices like DAP or DWA products. This is just information for you.
Can we can you what are you network needs that you want in a router. Maybe if we can get some idea about your needs, we can better help you figure out what is best for you and maybe also future proof your network as well. Any gaming, video streaming, large file xfers from places or torrenting, things like that and what are your WiFi needs?
I returned the 835 due to that I already had the 857 which does about the same on WiFi connections speeds, 450 UP and DOWN on both 2.4 and 5Ghz where the 825 only did 450Mb on 5Ghz and 300 on 2.4Ghz if I remember correctly. So was not advantageous for me to keep the router. I mainly wanted to experience the 835 due to others in your regional complaining out this router and not being able to watch youtube videos. It got to the point where I wanted to see if this was a regional ISP or HW problem. I got one and of course could not reproduce the problem here in the U.S. So we deemed it a problem between the ISP and this model router. Turned out it was a setting on the router that just needed to be disabled, was not a HW problem persae, since the ISP was not support IPv6 and this router does. Other than the WiFi not being as good as the 857, I really didn't see a lot of issues with the 835 and figured that with FW updates, it would improve and be a great router as the rest. I don't know for sure if FW has improved on it or not.
Yes the 8 series
L routers are all internal antennas and follow the DIR-645 antenna configuration. I have been enjoying the 826L very well and do mostly gaming on wired connections however I need to go back and reset the wireless connections. I don't recommend gaming or video streaming on wireless since both can be bandwidth hogs and it's my personal preference. However, I do understand that not everyone can run CAT 6 LAN cables all over the place so I try to test and real live wifi gaming and video streaming when I can. I'm currently testing a DIR-657 for WiFi performance. Then I'm going back to the 826L, this week I hope.