Sure enough, when I went to pick it up, The Cooling Shop had delivered a second Scythe Ninja fanless heatsink by accident. Bonus! Now I have one for my own machine for free :)
Just as an addendum, kissycat1000's new AMD Sempron x64 2600+ is running with that heatsink and an Akasa 120mm fan now at 5v (even 12v is very quiet - but not much airflow at either voltage) - usually the CPU is about 3 degrees above ambient when idling. Which is pretty bloody good. I'm now stress testing it with CPUBurn whilst defragmenting the disk (the only thing I'm not doing is exercising the graphics card) to see what temperature it will reach. After 15 minutes it's now at 9 degrees above ambient. I seriously recommend this heatsink to anyone who wants a quiet PC :)
Finally, del.icio.us is a fantastic tag-based online bookmark organiser. You can install an extension for Firefox that makes life great. No more annoyance at not having your bookmarks when you forget to back them up (whoops) or between PCs or browsers, and the tag organisation (which takes some getting used to) is far superior to organising by folder (think: ever wanted to put something in more than one folder, or share them easily with others?).