So you have 2 coax cables and 2 modems from uverse - and 1 is connected via telephone? RJ11? Cat3??
Clearly you have multiple networks setup here.. I have to assume the bottom one is natting and then the one on the second floor is natting, etc.
And for all we know your wireless routers are also natting.. Since you have not said anything other than your using as AP.. I find this like 90% not really accurate and they are natting, etc.
How do you have these N10P and E800 and your Wrt54g setup and connected.. Are they connected via lan, and dhcp turned off and your dhcp comes from both your uverse routers? If you want all your devices on 1 network you need to be using 1 router.. I don't really undersand the router with coax and then a router with telephone (dsl?) ?? What is the model number of these devices?
What exact powerline adapters do you have - I don't see anything with a model number of N200 in powerline products http://www.netgear.c...king/powerline/
As to where you nas sits.. Once your on 1 network, which should be a gig backbone does not matter where your nas sits.. Where do you want to put it? In the garage? At best those powerlines are 200mbps -- which they say they have fast ethernet -- so your talking like 90mbps maybe 95.. Why would you want to connect your server and or nas at 100mbit?? But seems all your N routers are only 10/100 as well.
What I would suggest is run an actual wire out to your garage if that is where you want to house your nas/server/etc And invest in at least a gig switch so your wired network can be gig. You can get a gig switch for as little as $20.. And If you want 1 network then you need to go with only 1 router or you need to put their lan on the same network and connect them via lan. Then you could use which ever you want for outbound gateway - but at a loss to why you would have both a coax and telephone connection?? That makes no sense and points to a dsl type connection - what are the model numbers of those devices?
When you connect to these uverse routers what are their wan IPs? Are they public or rfc1918? 10.x.x.x 192.168.x.x 172.16-31.x.x And lets get some model numbers off of them, and this box you say is outside that has both coax and telephone (you sure its not cat5, elephone would be cat3 with rj11 not rj45) Is there an actual device outside if so what is its model number.