Apparently, the SOC used in sansas was EOLed, and the newer ones use a cheaper and much less capable chip common in chinese music players. Attempting a rockbox port was deemed wasted effort. There doesn't seem to exist an off-the-shelf SOC comparable to the original.
The more expensive audiophile-orientated players use more power-hungry mips SOCs running linux, and the product is then designed to justify the expense and bulky battery.
