I worked around on WM-Port line-out for a while using with A726 and it must be compatible to any WM-Port walkman including X1000.
My DIY line-out cable built from Sony's DCC-NWC1 car charger adapter that has a line-out capable, eBay price is around$30-$40.
How to make it? Just follow the instruction:
1. Bought DCC-NWC1 and cut the cable at the length you desire.
2. Keep WM-Port side and throw away cigarette connector side.
3. There will be 5 wire in the cable shell, 2-big for DC charger and 3-small for line-out signal (bingo!!!)
4. Use your technician skill to solder the 3-small wire with the 3.5mm stereo jack, I recommend Neutrik as same as mine. Sorry for no detail here because I forgot and unable to open my 3.5mm connector because it filled it with resin.
I suggest not to break the WM-Port cover. Just use the cable that come with the port because the soldering contact in the port connector is very small and very very easy to crack especially with the big signal wires. I mention this because I lost 2 of them for my trial version.
What you get is more tight and bright sonic comparing to headphone output. You cannot expect this level of sonic with any iPod. I also have iPod touch and it far far away from my A726.

