Good to hear you are fixed up now.
When I went to upgrade my X (after 2 weeks!) the dealer (Bavaria) recommended to keep with the original speakers and upgrade the AMP (and crossovers). When the X5 first came out they had one from a dealer for two weeks and tried all sorts of combinations and found that for most people an amp upgrade does the trick. Maybe add a sub later.
I got them to install a Genesis Profile 4 which sounds truly amazing even at very high volume levels with no distortion from the original speakers. (OK maybe a little "woody" on the lower mids, I'm fussy with sound, component Hi Fi etc, etc.) So it seems that in the UK the place to start is with an amp up grade, then add a sub, then upgrade to really good speakers.
BSW have given me some advice on this as well, through this forum, and advised that with an upgraded amp alternative speakers to the BSW package should be considered. Micah suggested Alumopro (I think) but I'm still debating the sub woofer issue. A bespoke stealth box from the same dealer and Diamond speaker and Genises amp will cost about £1100 fitted, which is a lot of money added to which my wife likes the X5 so much I might lose it anyway!

Oscar