New FiOS GigE Wireless 'N' Router has slowed our wireless speed to a crawl...need help!

Question

This past Tuesday I installed the new N router.  Also, we upgraded to FiOS Quantum 75/35 (previously 15/5).  That was activated the following day.  I can't complain about the internet speed to our pc since it's wired.  Speed tests showed we were getting what was advertised. :-)
For the wifi, I can't figured out for the life of me what's causing our devices (e.g., our Nexus 7 tablets) to have a link speeds of 65Mbps one minute and then drop down to 5 or even 1.  The same situation was happening with my HTC Incredible II phone, but I think that connection was tapping out at 54Mbps.  The bottom would just drop out of the signal for some reason.  Other times we couldn't even connect back in.  The devices would say they're not in range even when they were in front of the router.  Not sure if I fubarred the router install or what?  I just swapped out the current Fios router for this new one.  Pretty straightforward.  At first, I logged into the router software with the defaults, but then I changed the the username, pswd, SSID, etc. to match what I used previously.  I thought it was working fine the night of the install but not so much after Fios got bumped up in speed the following day.  Maybe just a co-inky-dink?
I know you never get the same speeds compared to a wired pc but this seems worse (wifi-wise) than before the new router came along.  I've read that the 'N' routers can be finicky to set-up to run properly.  Maybe a setting or two is off?
I don't know if the fact that my son's netbook's wifi card is only b/g compatible would slow our network down?  At this point I'm grasping at straws!  I talked with tech support last night for 40 mins to no avail.  I got the usual story about wireless devices running slower than wired ones, that these smaller devices aren't capable to maintaining higher speeds (which I'm not sure I agree with 100%), the more active devices you have slows down your network, etc, etc.  I get all that.  But something is going on or actually, it's not.  LOL!
Why I don't agree with the above statement I mentioned is because I have my tablet at work now and the wifi speed is 54Mbps and it's constant.  So it seems to have no problems with this speed, unlike what I was told over the phone.
Let me know if I can provide any further technical details that'll make it easier to help diagnose our wifi issues.
Thanks for listening to me whine ,
-bill

Answer 1

Thanks for the help, Hubrisnxs.
Here's an update since I got home:
Nexus7 (N7) took a min or so to connect to wifi when I got home.  When it did, speed said 65Mbps.  So I ran speedtest.net and got 27/20.  Shortly after that I tried again but it was hesitating.  I checked the speed and it was down to 5Mbps.  Brought it upstairs to router and pc, and eventually it was back to 65.  Ran speed test a few more times with similar results.  I did notice that the connection would intermittently come and go.  Not sure why.  Looking at the wifi section  on my N7, it says our network is out of range and the N7 is 2' from the router.  Every now and then my network will go to the top of the list and it'll say it's obtaining ip address, then secured with wpa/wpa2 psk and it's locked in.  So I hit the connect button and it's out of range again.  Of course, while I was typing it decided to connect after 10-15 mins of trying/nothing.  Says, signal strength excellent, 52 Mbps.  Spoke too soon.  It's off again.  Crap!  Back on again but speed was 19, now 5.
I did check router settings and this is what I have:
Performance mode ('n')
WPA2 AES
Channel 1
nonbroadcasting SSID
Maybe I'll try channel 11 next.....
Just for the heck of it, here is the results from verizon speed test on our pc (wired of course):
Checking for Middleboxes . . . . . . . . . . . . . . . . . . Done
SendBufferSize set to [261360]
running 10s outbound test (client to server) . . . . . 34.66Mb/s
running 10s inbound test (server to client) . . . . . . 84.24Mb/s
------ Client System Details ------
OS data: Name = Windows XP, Architecture = x86, Version = 5.1
Java data: Vendor = Sun Microsystems Inc., Version = 1.6.0_37
------ Web100 Detailed Analysis ------
Client Receive Window detected at 1045440 bytes.
622 Mbps OC-12 link found.
Link set to Half Duplex mode
Information: throughput is limited by other network traffic.
Good network cable(s) found
Normal duplex operation found.
Web100 reports the Round trip time = 41.51 msec; the Packet size = 1452 Bytes; and
There were 72 packets retransmitted, 2254 duplicate acks received, and 2281 SACK blocks received
The connection was idle 0 seconds (0%) of the time
This connection is sender limited 91.83% of the time.
This connection is network limited 8.17% of the time.
Web100 reports TCP negotiated the optional Performance Settings to:
RFC 2018 Selective Acknowledgment: ON
RFC 896 Nagle Algorithm: ON
RFC 3168 Explicit Congestion Notification: OFF
RFC 1323 Time Stamping: OFF
RFC 1323 Window Scaling: ON
Information: Network Middlebox is modifying MSS variable
Server IP addresses are preserved End-to-End
Information: Network Address Translation (NAT) box is modifying the Client's IP address
Server says [] but Client says []
-bill