Is the TC my fastest option for streaming media files?

Question

I'm looking to set up a media server to stream content to all the devices connected to my home network. I know the TC itself cannot be used as a server but I have two mac mini's and I'll be running one at all times linked to either the TC or a usb drive. I'm hoping someone can point me in the right direction as to what setup would be best for the equipment I intend to use. Some of the video files will be blu-ray rips so they will be large and I guess my biggest concern is buffering issues.
My equipment consists of a fios router, 2nd gen mac mini running tiger, 2011 mac mini running lion, 2005 powermac G5 running tiger, latest gen TC, last gen airport extreme, last gen airport express, 3 ATV 2's, & 2 ATV 3's.
My house is a split level so it's basement on one side,  5 stairs up to ground level on the other side, 5 stairs up to living room/kitchen above basement, and then 5 stairs up to bedrooms above ground level. The router is located in the far front corner of my basement along with the TC, G5 and 2nd gen mac mini. The newer mac mini is located at the far back corner of the ground level along with an airport express. There are 3 ATV's in the bedrooms above the ground level, one in the living room, and one in the basement. I have the airport extreme with a 2TB usb drive located in a utility room pretty much center of the house in the basement. For the last year or so my setup was the airport extreme connected to the fios router using cat5e. It was configured to create a network and then I had the airport express (not wired) configured to extend the network. The signal was pretty good throughout the house but I would sometimes have buffering issues on the ATV's for the bedrooms. I figured it was because I was either using the usb drive connected to the extreme to store my media files and loosing speed there or that the ground level floor is cement and the extreme signal was having a hard time reaching the express. The TC is a brand new addition and I figured moving my media files on it's internal drive would be speed things up. Also I will now have two devices I can reposition to extend the network.
As of yesterday the new configuration is the TC creating my network connected to the fios router with cat6. I still have the extreme in the basement in the utility room only 15 ft away (I'm still using the ethernet ports for my 1st gen PS3 and sonos system). It's configured to extend the network and it's not hard wired but I do still have the cat5e ran to the utility room from where the fios router and TC are located. The express is still on the ground level not wired (can't run wire to that area) and configured to extend the network. I do have 2 other cat5e wires ran from the fios router/TC location to the utility room. I'm not sure if they were secured when I had the basement finished so I may be able to use them to pull cat6. There is a shaft from the utility room in the basement to the attic above the bedrooms. I have the ability to run them further and locate the express in my attic if I need to boost the signal.
Sorry for listing so much but I wanted to try and give as much info as possible. I've probably got a few options here but what I'm trying to do is leave the mini's in the locations they are right now and I need at least 2 wired connections to the utility room for the PS3 and the sonos.
Any recommendations would be appreciated

Answer 1

I don't have time to give a complete answer.. and I think I read your first post a while ago and really got lost.. sometimes it works against you giving the full story if it looks like a thesis.
A few basic principles..
1. Wireless is a shared media. It cannot talk to two different devices at the same time.. each one gets a time slice. More devices.. less slice. But it is worse than that. It cannot transmit and receive at the same time.. obvious if you think about it. So it is half-duplex.. it is either transmitting or receiving.. tx or rx. When you do wireless extend.. you halve the speed.. aprox. So each packet is double handled. It is not able to tx across multiple routers at once. End result.. Avoid wireless extend (repeater in normal terminology).
2. Roaming network is much preferred but there are limits to the number of channels especially on 2.4ghz.. effectively just 3, The only non-overlapping channels are 1, 6, 11. So if  you use wireless devices in range of each other, they must use different channels otherwise they interfere with each other.
3. 5ghz has more channels and faster speed.. in latest equipment.. much faster. The latest TC is 450mbps on 5ghz. But you need wireless that can receive that speed to make use of it. The other side of the coin, is the range is very poor.. only one room next to the equipment gets full speed.. next room ok.. after that generally 2.4ghz is faster. Apple routers are not RF power house.. I can barely see the signal in the next room. 
4. Ethernet cables are the best. Use ethernet everywhere. Cat5 or Cat6 makes little difference. Both can do gigabit .. just the distance is limited on cat5 but you will seldom see that. Ethernet networks have opposite characteristic of the wireless network.. it can talk to multiple computers at the same time.. it can tx and rx at the same time.. so it is hugely better.
5. Multiple access to the media store is going to stress the computer hard drive access speeds. As I see your layout, you could be streaming multiple programs at once to different rooms. Even a purely ethernet system will have issues.. if you expect multiple bluray rips to run to multiple locations at the same time. Over wireless it just isn't going to work.