Q: Help with Best Wifi Setup

At minimum, assuming that you want a decent quality signal on each floor, you will need a total of at least 3 AirPorts....one centrally located per floor.....or....if you don't need coverage for the entire floor, then the AirPort would be located in the middle of the area on each floor where you plan to use wireless.

Ideally, you would use the same AirPort Extreme devices on each floor.

For the best performance by far, plan to connect all of the AirPorts together using a wired Ethernet cable connection. For example, if the AirPort on the first floor will be your "main" router, then the AirPorts in the basement and upstairs would both connect back to the first floor AirPort using Ethernet cabling.

.....but do not think I will buy 2 more cable modems to hook up in those floors and then in turn purchase 2 more AirPort Extremes to them (I think this is what you were suggesting).

No, I was not suggesting this at all. You only need one modem, and that connects to the "main" AirPort.

You think I can survive or obtain a decent signal if I just get an extre in the top floor and basement and just extend the network?

Yes, if you connect both the top floor AirPort and basement AirPort back to the "main" AirPort using a wired Ethernet cable connection.

No, if you are asking if the top floor and bottom AirPort connect using wireless.  There are good reasons for this.

1) Even if you have line-of-sight between the extending AirPort and main AirPort, there will be a loss of at least half of the maximum speed on the entire network.  Nature of the beast when you try to extend using wireless only.

2) A ceiling is, on average, about 3-5 times thicker and more dense than a wall. There will be a significant amount of loss as the signal attempts to pass through the ceiling.  So, the extending AirPort gets a much weaker and slower signal to try to extend.

Sure, you could try to use wireless to extend.....and it might "work".....but the network will perform at a fraction of its capability. But....don't take our word for it. Here is what the Apple support document on extending says about this:

Extending the range of your Wi-Fi network by connecting Wi-Fi base stations together using Ethernet is always the best option, and will provide the best throughput. Ethernet offers up to one gigabit rate, which is much faster than wireless (for wireless, the maximum rate is 450 Mbps on 802.11n @ 5 GHz). Ethernet is also resistant to radio frequency interference and is easier to troubleshoot. Additionally, as there is virtually no management overhead over Ethernet, more data will move from one point to another in the same space of time.

Wi-Fi base stations: Extending the range of your wireless network by adding additional Wi-Fi base stations - Apple Suppo…

I will have to agree with Bob on this, location is all, and you need 3 locations to properly cover a 3 floor house (at least)

If you are saying that you already have Ethernet cabling run to various rooms in the house, then all of the Ethernet cables will run back to a central point or equipment panel.

The modem and your "main" AirPort Extreme will need to connect to that equipment panel. So, if the equipment panel is in the basement, for example, then your "main" AirPort Extreme will be in the basement.

So, you would connect an AirPort on the main floor to an Ethernet wall port and the an AirPort upstairs to an Ethernet wall port. That will connect the main floor and upstairs AirPorts back to the main AirPort using the Ethernet wiring in the house.

If this all sounds a bit confusing, it would be best to consult with a computer guy to help you with the installation and set up of your network.  The "Geek Squad" at most Best Buy stores have experience with this type of installation and set up.

Then, you will need to decide on whether you want to run Ethernet cabling to allow your network to work at its full capability.

If you cannot run the Ethernet cable, then it might be possible to use Ethernet over Powerline (EoP) adapters to send the Ethernet signal over the existing powerlines in your home.

The theory with these devices is that you already have the wiring in place, you just need the adapters.  This type of setup will not work as well as simple Ethernet cabling, but it would still be far better than trying to use wireless to have the other AirPorts extend the signal.

The bottom line here.....and, possibly information that you do not want to hear......is that trying to use wireless to extend a network is the worst possible choice in terms of performance and reliability.

You can use separate modems for each floor, with separate wireless transmitters, care will be needed to keep their IP ranges separate though. It would be preferable to run ethernet cabling and use that instead.