Emolpus - I haven't tried using it, but there's a project on Sourceforge to build a manager-equivalent for Linux.
http://ifpgui.sourceforge.net/
You will have to flash the player firmware to IMM version. Then you can record up to 320kbps again. As I understand it, the IFP processor isn't fast enough to encode at > 96kbps and also write to FAT-formatted flash memory. Writing to the proprietary Iriver memory format is presumably faster, so it can encode at a higher bitrate.
Give ifpgui a spin, and let us know how it works for you.