Most likely around that time, yea. Possibly fall/winter 05. Louise could have picked them up on her first shopping trip and they just worked out better for the blue suit later, too. Most likely not older than that, though.
And yea, the Kenzo is the only tie that can't be seen in any pictures. There was one picture in a making of Who book that I saw once where Tennant was wearing a birthday hat and had the jacket open, but the picture went off the bottom of the page right where the jacket normally covers it up. If you could track down that full picture, it would be very helpful.