Redoing Network Completely

Our Current setup is using the Netgear RangeMax WPN824. The issues are not that it cannot cover the entire house, but that it crashes when to much bandwidth is pushed by the Mac OS X computer. It has to be power cycled or it does not transfer data at all through any computer, and the entire network goes down. A quick fix we tried was switching to B band, and it did not work.

Our house uses
2 Sony Vaio's(XP) Laptops(A/B/G)
1 Dell(XP)(A/B/G)
1 Wired HP PC(XP)
1 Macbook Pro(OS X Leopard)(A/B/G/N)
1 Wireless Xbox 360 w/ Live(B/G)
3 Iphones

We Need All the computers to be able to get online throughout the house(9000 Square Feet, 3 Levels). We also want the pool to have wireless access, which is ~110 feet away from the bottom floor back door. The Modem/Router is on the 2nd floor of the house.

I was planning on getting the new AirPort Extreme Base Station with Gigabit Ethernet, to ensure compatibility with Mac OS X, but it is very expensive and I'm not sure I see it as the best solution. I think we need a router with some type of range extending extra equipment. Can anyone explain to me what the best way to cover the area completely while maintaining compatibility, Hardware suggestions are appreciated, and price is undecided, preferably under a few hundred for all the equipment.

The Airport Extreme is really cool, really expensive, but only average in range coverage. It is not more compatible to the Mac OS platform than any other router. It does make it more difficult for non-Mac OS machines to configure the router, though, as the configuration is not Web-based. I'm not anti-Mac, I'm a Mac user myself, but I want to be fair in my assessments. It sounds like you actually need a bandwidth limiter instead of a new router. This can usually be done by adjusting the router configuration, if the router allows it. Maybe you can look through your router settings and let us know what you find?