oh...samsung epix...I confused it with Samsung Epic lol...same difference...
If you want to look at the options go here:
PDAdb.net - The Best Smartphone, Tablet, PDA, Netbook, PNA & Mobile Device Specifications Database
it has all the phones there, you can use the pdachooser, pick Windows CE and then keyboard.
Though off the top of my head I would guess the highest spec one is the Motorola ES400S.
Keep in mind the processor mhz is important but a Cortex A8 will destroy a ARM11 processor even if the Corex A8 is clocked at half the mhz.
Edit: The Samsung Omnia Pro seem to be the successor line to the Epix, they have same processor thats in the ES400S based on the Cortex A8