Asus RT-AC68U vs. RT-AC66U routers?

My D-Link DGL-4500 seems like it is deteriorating (and I began to dislike it shortly after I bought it.) It's time to consider a replacement. I'm thinking if I get one now, I should go with an ac router. And it MUST support DD-WRT or other open source firmware. I really get tired of my DGL-4500 rebooting and no FW update form D-link and no DD-WRT. But enough for my reasons.

It seems one of the highest rated routers for is the Asus RT-N66U and it does support DD-WRT. It seems that the natural step up from that is the RT-AC66U. It seems to get good reviews on both Amazon and Newegg. There's an update from that, the RT-AC68U which looks like a refresh of the 66. It has USB 3.0 (which I don't plan to use - my printer has an Ethernet port and I have a separate NAS.) It looks like the arrangement of the ports is better on the 68. The 66 has them between the antennas and I'm thinking of hanging this on a wall.

One benefit of the 68 is that the Egg has a combo deal right now with a Moto Docsis 3.0 router. It's about time to replace my Docsis 2.0 modem. Comcast tells me it is no longer supported and one day they could turn off backward compatibility.

Any thoughts on either of these and choosing between?

FWIW, I just spend $17 for an Edimax EW-7811UTC for my 5 year old Thinkpad because it could no longer keep a connection. I wanted to know if it was my AP or the TP WiFi card and it seems to be the WiFi card.

I currently have the AC66U and it's been just fine for the apartment I live in. We've got a pretty long apartment and everyone gets good signal throughout the apartment. We also went with a Docsis 3.0 modem (SB6121) and it seems to be doing its job. I read a lot about signal dropping and connectivity issues, but we don't seem to have any problems.

The only issue I ever notice with the Wifi is that ever since I updated to Ubuntu 14.04, I can't SSH tunnel to my school's servers anymore. I can connect just fine and it works for a few minutes, but eventually the connection will time out and my terminal stops responding. I don't know if this is a wifi problem or an Ubuntu problem, but using a wired connection has no problems. My current theory is that the wifi briefly disconnects and reconnects, and the SSH protocol doesn't quite know how to handle it. At this point, I'm chalking it up as an Ubuntu issue, but do what you will with that information.

I pulled the trigger on the combo modem (Moto SB6121) and AP (Asus RT-AC68W) and got them set up last night.

Wow! Just wow! I cannot believe how much difference this made in network throughput. Using the old AP, only two of my devices could saturate the expected bandwidth of a DOCSIS 2.0 modem. Other devices fell below the 20Mbps that Comcast was giving me. With the new modem and router, all devices are saturating the WAN connection. You can see results of some tests here: https://docs.google.com/spreadsheets/d/18rqE-7W5K38MmqxzX4SwHOeLnlYJPYAkvCdhXE07JNo/edit#gid=0 The interesting thing is the improvement in 802.11n devices since the previous router was also n (and dual band IIRC.) And since it was marketed as a gaming router, I expected better performance. (Last DLink product I am likely to buy. )

I did further tests to evaluate the bandwidth for file transfers. I went between two machines that both had SSDs so hopefully drive speed would not be a factor. I did try to test throughput transferring my 333MB test file locally through an ssh connection to the local IP and it took about a second. I don't think disk speed was a factor.

I'm even wondering about whether or not the internal WiFi on my Thinkpad is really bad. It seems to be working fine with the new AP.

That's awesome to hear. Glad you like the new stuff!