Hi phantom_zero,

If you are looking for modem router with dualband, we got one model DSL-N55U.

http://www.asus.com/Networking/DSLN55U_Annex_A/
SRP is RM420.

It has a function called QoS and it apply to both the band when it is turned on.
If you are looking for a budget wise modem router, you can have a look on DSL-N10E.

SRP is RM95

If you are looking for performance modem router, DSL-N55U will be your choice.
Thank you

Hi phantom_zero,

5Ghz Will have better transfer rate compare to 2.4Ghz. But the down side is 5Ghz will have lower coverage area.

You can turn on the QoS, once turned on, it will have higher priority on Gaming and Surfing net.

And like I said, I don't think there is a lag free modem router out there. It need to depend on the Internet line also.

Thank you