If you have to use 2.4ghz NanoStation M2 units are still a good choice.  I've migrated a lot of my stuff to 5ghz where I have good line of site and used a lots of NanoBeam M5-16 units.  I think I have 8 of them on my network.  What are you trying to accomplish?  What's the distance?  How is the line of site?  Can you get higher to get over the stuff?

I just set up a link yesterday that goes 5 miles with a NanoStation M5 to a Rocket 5 with a sector antenna.....link is very slow but I have a PowerBeam coming to replace the nanostation with.

I told my wife last night that I would like to upgrade all my stuff to the new AC line of products.  Only 5ghz is available but it is WAY faster.