i have a v630. i flashed it to k610. then to w660, but because of all the bugs, i flashed it to k530. i don't see any motives to flash to w660, because of all the bugs. for me, now the k530 firmware is the best. i am 99.99 % sure that you can flash k530 to w660. give it a try. a liked the flash menus. they are awesome.
best regards
the walkman is pretty cool too