Another Panasonic vote. My old Panasonic is 10+ years old and still the best cordless I've ever used (900mhz). My newer one is a bit sexier looking, and includes a fax/answering machine/speakerphone @ 900mhz too. Its still very good, but not quite as clear as the old one. Obviously no interference with the wireless.
If possible, test the new phone before buying it. Not so much for range, etc, but if I had tried the newer one, I would have realized that the buttons on the back of the headset can hang up the phone if I hold it to my ear with my shoulder. Now I just use a headset anyways, so it is no big deal..