Why can't I get TC or Airport Extreme to work in my house?

Question

I   am very mad at myself for buying a TC in April and now the new one is out!!  I had issues with connectivity with my Airport Extreme and purchased a TC in April thinking that the APE was on the way out and now the TC is doing the same thing....help!!
I live in an old house with lathe and plaster walls.  The TC is in a closet on the stairwell that is central to the main floor.  We have about 75Mbps download from Comcast but the wireless was getting flaky.  Our iPads, and phones would just loose connectivity and a speedtest.com test would show maybe 6Mbps when we had the APE so we figured the answer was a new router.  After we started seeing some of the same issues with the new TC, I have changed our set up to using the TC as the base station and have the APE (old one) set up in the livingroom as an extention. 
I am still not sure this is the best way to run this and am really mad that Apple upgraded just after I purchased the TC. Should I just sell the TC and get the new version with hopes that the new antena will help my problem?? 
BTW, I work for IBM from home so I really need the internet to work to the max in order to get my job done. 

Answer 1

I work for IBM from home
Kind of ironic.
I   am very mad at myself for buying a TC in April and now the new one is out!!
It is the nature of technology.. whenever you buy you are going to be caught by the next wave of products.. let yourself off.. Apple are the most secretive company in the world. Although I was telling people to wait for a fair while before the announcement.
I live in an old house with lathe and plaster walls.
The heavier the materials and the higher the moisture content the worse wireless. Older houses often have water problems..
There is no certainty the new AC model will fix your problems.. and certainly not without AC clients.
If you have a 75Mbps connection my first test would be ethernet to the TC and test if you can get that.. wireless turned off on the computer and no other clients turned on. Make sure the TC is actually routing at full speed.. people have found the TC can be slow.
If the ethernet test fails, replace the TC with another brand router.. eg Asus or Netgear.. ones that take 3rd party firmware are my favourites..
Relegate the TC to backup duties in the local lan by bridging it to the router.
If ethernet is fine and wireless fails to connect fast enough.. do a proper wireless survey in your home.. use a wireless analysis software.. I don't know the paid one for Mac but istumber is ok.. inssider on pc is really good.
A full spectrum analysis would be even better but that requires more specialised stuff. But turn off everything you own that is wireless.. cordless phones, av senders, door bells, baby monitors, and the zillion other things that use unlicensed bands.
Do a full reset of the TC and set names, short, no spaces and pure alphanumeric for both 2.4 and 5ghz bands.. different names.. and set fixed channels and test each in turn.. non-overlapping at 2.4ghz, 1, 6, 11
For 5ghz down low, 36-40 and one of the high channels is enough.. 150 or greater.
If you own the house and you do work from home.. run ethernet.. and claim it on tax as business expense..
Anybody running business should run ethernet.
Wireless is for toys and hobbies .. the reliability of wireless is really not up to business standards. At least IMHO.. !!
If the business run wireless.. it comes with products that have the big C on them and cost thousands of dollars. Ask at your local Apple store what brand wireless equipment they run.. it aint apple.