If you already have an iPod, the Wadia can make sense. Several companies offer mods (starting around $375) to reduce jitter and upgrade the power supply.
But if you don't have an iPod (or don't want to deal with the limited storage and eventual battery life), the Squeeze Box (or Duet) wins. Like the Wadia, stock SB/Duet units aren't considered high end.
Either way its about a $1,000 USD to mod and upgrade the power supplies plus you'll need a computer and probably add one or two hard drives for storage and backup.