Just some things to think about...
a) I believe the setup for the TC1000 is the same as the TC1100 in that there are two slots, only one is user accessible. I was worried at first when I got mine (I didn't know about this site and didn't see this fact before) and thought I had half the RAM I really did because I only saw the one 512 (mine came with a GIG). So you have 1 non-user-accessible slot with 256 and in the accessible you will add the 512.
This would be the best of all the choices you mentioned, IMO.
b) You didn't give the specs of the drive it comes with but I have two TC1100 and one has 40GB 4200RPM and one 60GB 5400RPM and I don't see that much difference in speed (until the RAM gets used up).
c) Unless you have a super fast connection 11Mbs is plenty. 54Mbs is over kill if your network is 1-5Mbs. Unless you have FIOS connection I would think RAM upgrade is better than wifi.