I really struggled for a decent 26.4 seatpost for my GT - bought a BBB one off ebay for £20 in the end (although I have seen them cheaper now). 2-bolt design and 400mm long, seem pretty good!
I think it's really nice quality. Medium weight, brass bushings where the bolts are tightened. Not delicate but not over-engineered. Someone had one on the Peaks ride too (similar problem finding the 26.4 size) and he was 6ft plus with a lot sticking out the frame and he was pleased with it too.
Not seen the Brand X one myself. BBB stuff is generally pretty nice, a company that seems to supply those bits and bobs you sometimes struggle to get.
Would certainly buy another.
I've got that elusive seatpost in 26.4. From an Orange, cromo and in great shape. I'm holding it for someone at the moment, but if you are interested, let me know.