New tivo set up but slow wireless speeds now???

Now that my new roamio plus and two mini's are up and running everything seems to work great on the built in moca network. but now im having wifi speed issues. i'm wondering if this can be caused by the load of the tivo taking that last open ethernet port on my router?

When Indo a speed test now im pulling 17.5 mbps on my standard TW 15 MB plan.
But when I run a speed test on my ipads im flucutating. If I reboot the router Im upmto 7 mbps in the same room as the router. Worse yet, 15 min later when I ran another speedtest Im down to 1.9 mbps!

Im using my own equipment:
2 year old Netgear range max wirelsss N gigabyte router model WNR 3500 OU
2 year old Motorola surfboard modem model SB510 IU

Does anyone think my fluctuating and low wireless speeds might be due to adding the tivo and taxing the router?

Or is the router just going bad?

Plugged into the 4 ethernet ports:
Magic jack
Home alarm system
Mac mini computer
Tivo plus

For devices connected to the network (but there are only 2 of us and we dont run many at one time)
2 samsung smart tv's
2 apple tv's
2 ps3's
3 ipads
2 iphones
Netgear range extender

If it is my router failing I've owned several brands and Im now partial to netgears products and good c/s

Any router recommendations?
Is this netgear model below overkill for my situation? I might raise my internet speed plan in the future if need be.

http://ift.tt/1MJEGWm

Thx