They stock the full range of imates etc...
You have been using a Dopod so you will want somthing running windows mobile 5.
HTC is also available but i have only seen it in the Airport duty free.
There is also a small cell store oposite the food palace in Al Saad that stocks imates.

If you want to sell you mobile head into the Al Saad mobile area off Al Saad street.
They might take it off your hands.

Good luck!