Time Capsule and Thomson modem/router
If you connect to the TC (via whatever speed you can get with wireless, or gigabit cable) then your communication to it and any other device on teh same LAN that is also connected to the local LAN is unaffected, it is only when you wish to send traffic over the 100mbit modem connection that you will be limited to it's speed, so basically your internet will be limited to 100mbit, and so long as that is faster than your ADSL/Cable connection anyway, then you will never notice it.