Difference amongst liteon dvd drives?

Lite On lists a few 16x dvd 48x cdrom units on their page, the LTD-165H, LTD-166S, and LTD-163 (D)
The only difference I found amongst the descriptions were that the 163(D) doesn’t have DVD-Multi, but they both can read the same kind of dvd media. Anyone know what the difference is amongst these drives, and which is best for reading cds to copy?
Also on the 163, what do the models with the D indicate?

I am also interested in this difference as I just placed an order for the LTD163 @ googlegear.com for $40 shipped. For $41 I could have gotten the LTD165H but w/out free shipping. Both are retail and list what seem to be identical specs, is there a difference I am unaware of? Anything significant enough to warrant the extra cash? Thanks!

LTD-165H reads Multisession DVD and all DVD formats.
And it’s shorter than the LTD-163(D).
D was added when parts used in the LTD-163 were phased out, and so they had to remake the drive to comply with the new parts. So they called the new drive LTD-163D.

For anyone who has a 40125 or 48125, and a ltd-165 or ltd-166s, does the 165 or 166s slow down (and get quiet) like the 40125 and 48125 when playing audio CDs? I have a 40125 and would like to get a dvd-rom too, and I’d like it to be quiet when playing audio CDs. Is this the Smart-X that does this?
I just returned a ASUS CD-S520 because it seems to run at full speed when playing audio CDs and is MUCH louder than my 40125.

Oh I forgot, how about the ltn-526? Same question as above. I don’t really need to read DVDs, just CDs. They all have Smart-X, so they all slow down to just the speed they need, right?