This is the very time when you may find some highly reduced Xbox prices, as the current 2 month trial offers are ending & those xbox cartons that are badged with the trials info will be being sold off cheaper. Gameplay just sold them for £99.
Any new boxes wont be around for a while yet & I think that everyone will suggest that you just get one now & dont wait - its not worth missing the fun.
Get a box, get Xbox live (if you have broadband - if not get that too) and get enjoying yourself.
