If you are rewiring now I would definitely go for Cat6a (or even Cat7 / 7a) simply because there is little difference in cost and it will keep you sweet for many years to come. Also remember the basic rule of socket placement - you will need twice as many as you think! I helped a mate wire up his home with the switch in the garage and cable (only cat 5e unfortunately) throughout and we ended up having 4 outputs in the lounge and 2 in every other room. Costs little to do now - saves much heartache later!
Best I can get for cat7 is 1.8k/500Mtrs (no other sizes available here in Singapore). Cat6 is around Sin$180/100Mtrs while cat5e is around S$70/100mtrs. Cat6 cable in the UK from the same supplier is around S$140 . I am back in the UK this weekend for a family visit. Not sure about packing 100mtrs of cable in the suitcase though .
Interestingly, fibre optical cable is around the same price as cat6.
RB