Airport Extreme/Time Capsule Network Design Question

[snowyeti]

Setting up a friends Apple network, and I'm wondering about the use of the WAN port on the devices.

Background, there is one time capsule at one end of house, and another airport extreme 802.11n on other side of house.
There are 3 Airport Expresses for sound connected as clients (Thankfully no WDS). There are about 10 nodes with
a bunch of 802.11b/g and 802.11b/g/n. 3 machines which have 802.11b/g/n run time machine backups.

Any difference between Scenario 1 and Scenario 2?

Scenario 1 (Currently deployed)
______Port 4_______WAN________LAN1___________LAN1___________
[ADSL Router] <--10/100--> [Time Capsule] <--10/100/1000--> [Airport Ext]


Scenario 2
_______Port 4_______LAN1________LAN2___________LAN1___________
[ADSL Router] <--10/100--> [Time Capsule] <--10/100/1000--> [Airport Ext]


Now ideally I'd like to have Scenario 3 running, but because the ADSL Router is only 10/100,
this means if a mac was connected to the airport extreme and a time machine backup started, then
this would significantly slow down the network. Agreed? Other alternative is to buy a 10/100/1000 ADSL router/switch

Scenario 3
_______________Port 4___________LAN1
[ Netgear ] <--10/100--> [Time Capsule] ---> Wireless
[ ADSL Router ] <--10/100--> [Airport Extreme] --> Wireless
_______________Port 3___________LAN1

Thanks