For those who are interested, I have 3 AirPort Extreme Base Stations and 1 Time Capsule Base Station plus 1 AirPort Express Base Station (all capable of 802.11n network) in this house.
The house is not that big, but the multiple base stations (in roaming network setting, except the AirPort Express) provides great signal coverage around the house.
If I just have one base station and placed in the centre of the house, it should probably provide enough coverage, however, I wouldn't expect a good coverage, hence, I went for multiple base stations.
The Mac Pro is connected to AirPort Extreme Base Station with a cat.6 ethernet cable and (bridged) 802.11n WiFi network.
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