I recently got a 6320i and like it very much. It probably has a few more features than you really want such as camera, music player, and radio. This drags the standby time down to 3 or 4 days. But it is roughly the size of the 8310, does triband, GSM, and bluetooth, and it takes up to 1GB memory card (Nokia say 512MB, but 1GB works okay). Plus it "just works" (TM).

I can read the screen on mine in daylight. But we are talking feeble, washed out, UK daylight. Proper NZ daylight might make a difference.