I doubt it will double disk transfer speeds; this is more throttled by the I/O cycle time - it's not an ISA bus, and cycles are slower - the fastest ARM-based hardware we have will manage about 6MB/sec from disk into thin air. Multiple sector transfers per IRQ helps a bit, but not a huge amount (in our testing, anyway). The ARM tends to have better IRQ latency than x86 boxes.

The car player's I/O speed configuration is a bit conservative, and can be inched up a bit - however, the player doesn't need this so it's best left alone really...

Hugo