I hope someone would have given you a more informed opinion. I am looking for some pc4000 (2x512) memory also.
Geil is cheap, but i have heard wayyy too many people having to RMA their's. A lot of people are selling Geil in the forums cus they had to RMA it and in the meantime they alreayd bought another memory, and now they are selling their new ones that they got.
So personally, I am skeptical as to run Geil. PQI and Patriot are supposedly good or get the job done. If I were you, I would try PQI or Patriot. Get the 2x256 and run them in dual channel rather than a single stick.