Shimano XT or XTR from one of the German websites is probably the cheapest way to go. XT is pretty darned durable these days, I've an XT BB that's approaching thirty months continual use and another that's clocked up twenty four months on one of my other bikes. When it dies, I may well spend a bit of cash on a Hope stainless steel replacement, but or the sake of what has so far amounted to a pound a month I may well stick with Shimano.
I've never tried FSA, but RaceFace BBs are absolutely dire - one died on me within three months during the summer of 2006, which was notable for it's almost complete lack of any precipitation whatsoever in my neck of the woods. I was so spectacularly unimpressed with the longevity of my BB and the (then) quoted thirty quid for a replacement that it's been Shimano ever since.