There shouldn't be any sound difference regardless of whether it is rosewood or bamboo, Audeze chose the right material so it retains the usual Audeze LCD2 house sound, it wouldn't be called an LCD2 is there was any sort of a marginal difference between the two different material based LCD2's for that matter. Weight difference, the bamboo are definitely lighter but they are also more stronger and reliable than the Rosewoods which is why Audeze made the change to a different housing material after learning the mess from the early Hifiman HE-5LE's and the early rev.1/rev.2 cracking.
Move onto the comparison.
The HD800 extract/offer the best and the most detail of all the 3 mentioned headphones in this thread. The slight treble peak can be of annoyance to those with sensitive ears but some mods and a higher grade warm amp can sort the problem out. It also offers the best soundstage/imaging of all of the 3 headphones as well, if you listen to classical, jazz none compares to the HD800's.
Regarding with people saying they are bass-light, they are not. Either that you're a basshead and used to the flabby basshead headphones widely available on the market or you don't have the right setup, I will say it again, to get the HD800's short of acceptable performance you need to have high quality source (music files/transport system/high end dac) and a very synergising amp. If you think you can just enjoy music on the HD800's powered by an O2 or Lyr, think again because I've heard it and it sounds crap, not saying the amp's are bad but the 800's are finicky when it comes to amplification. The Crack + Speedball powers the HD5xx/6xx/800's wonderfully and my honest opinion is that it sounds marginally better than any of the Woo WA6/22 combo I've heard.
Right onto the LCD2, regardless of revision, the LCD2's are very laid back (dark, warm) signature headphones. They sound thick and sometimes congested sounding compared to the HD800's. By congested I mean by for me I listen to some custom mixed electronic music with sometimes over 10 layers of various sound effects going off, faster based electronic the LCD2's sounds at times lacking air to catch up and so therefore can sound rolledoff. But they do have very impressive bass performance, I wouldn't exactly call them completely neutral but they try to imitate the neutrality of what you're supposed to be hearing from your source. Amp recommendations for the LCD2's is something bright or borderlining warm, certain tubes I don't recommend because the low-ends will sound flabby and too warm sounding restrictive. Though they are easy to drive and forgiving on the recording.
HE-500's, I've had a small amount of headtime experience with these and the HE-6 so take this with a grain of salt. The HE-500's are not bad headphones not exactly what I'd call up to the level of the LCD2's (imho) but both are directly comparable in certain aspects, the HE-500 are tad brighter than the LCD2's, does not exhibit the congested feeling I have with the LCD2's when listening to complex mixed/fast music, but the LCD2's have superior bass response compared to the HE-500's. HE-500's also don't require alot of juice to get the right ompph to sound right, fairly easy to drive and sound well as well, would like to pick these and the HE-6 up one day and give it a thorough listen but my favourite Hifiman has been the HE-400's so far. I feel the HE-500 offer tad bit more detail over any of the LCD's but again take this with a grain of salt.
The HD650's are not far from the HE-500/LCD2's in terms of performance, but I'd pick my HD600's over the HD650 anyday unless I had a SinglePower xds amplifier.
Hope this brief impression of mine helped.
buttt so much money and I'd probably get a another headphone first like the hd800 before getting another amp :O or buy a better dac which seems to be diffcult to distingush around here if its worth upgrading I currently have the dragonfly which is an awesome dac... 