I've got the linksys WRT610N I'm very happy with it
It has both 2.4GHz & 5GHz & manages them at the same time so you can do multiple networks and for wireless speed it's rated @ 300Mbps.
I haven't flashed it with DD-WRT and I probably won't as I have no issue with the stock OS because it's easy to navigate and use.
Atm I'm using 2 desktops (wired) & 2 laptops with wireless N and it handles all with ease
I hope this helps you out and good luck with whatever you choose mate
