Asus RT-n66u poor wireless

[#1]

Hi,
Having read about the poor wireless signal on the free 2704n router I decided to buy the Asus RT-n66u to replace it.  I swapped it over today and getting similar speeds but the wireless signal on the Asus is worse than the 2704n.  I have a PS4 upstairs (router downstairs) and the Asus is getting 50% signal, whereas the 2704n used to get 64%. 
I thought the Asus router is supposed to be great for wireless reception so I'm a little confused.  Is there something I missed setting up the Asus, if this is as good as it gets, I'm going to replace the original 2704n and return the Asus back to Amazon.
Any help would be much appreciated.
Thanks, Jason

[#2]

I think I'm going to try to update the firmware to merlin.  Trouble is I'm quite the newbie when it comes to routers and afraid off bricking my modem.  Could anyone give a step by step explanation of how to upgrade the firmware to the best merlin version?
Thanks.

[#3]

If you're looking for the best wi-fi performance then I'd suggest going with this version of the Merlin firmware http://www.snbforums.com/threads/fork-update-for-374-43-available-v13e1.18914/
Flashing is very straight forward and this version is very stable - I've been using it for several months with no problems. You flash it like any other version of the firmware but you'll probably need to do a factory reset which is explained in posts #2085 to #2092 in the thread I linked to above.
Bob.

[#4]

Thanks for the help Bob, much appreciated.  I'll give it a go tonight 

[#5]

Good luck, let us know how you get on.

[#6]

I can also vouch for the Merlin firmware and its ease of use/installation. It also fixes a few annoyances (like Dual WAN not working properly).

[#7]

Just an update.  I managed to install the Merlin firmware suggested above, but although the wireless signal was more stable it still wasn't as strong as the PN free router  :-\.  I've been messing around with it for a few days and couldn't improve it.  Tbh I think the Asus is a little too specialised for my uses anyway, so I have sent it back to Amazon for a refund.  I'm now happily using the PN router which seems to work well in my set up.
Thanks for the help guys.