Not sure "search" would work for at least part of this question.
Amazon provides a selling platform for quite a few dealers, and you sometimes will get more than one listing for a particular product. I don't know how the products are initially set up, but I suspect one dealer has the product listed as "M1000/M1001" and the other as just "M1001" so Amazon creates separate pages for it. They should be on one page.
When you look at the listings themselves, you'll see a different "sold by" name under the price. Read the feedback for each dealer by clicking on the name; I choose mine after seeing that one dealer responded quickly to complaints posted there, while the other never did.
The phpBB search function returns nearly everything with any of the words in it; I've found it mostly useless unless you want to do hours of reading posts. I do search the forums using Google with "site:rokulabs.com" as the first part of the search, and then the search phrase. It works much better.
The first hit using "site:rokulabs.com differences between M1000 and M1001" as the search phrase in Google brings up this post (!) and then the fourth result is at http://forums.rokulabs.com/viewtopic.php?p=54249
1001 is the newest model, and may still be errantly called the M1000 in many places (even here on the fora). 1001 has jacks on the back, instead of on the end, consequently the endcaps on the M1001 are fixed, and removeable on the M1000. M1001 wireless is on-board the chip, M1000 uses a WiFi compactflash, again under a removeable endcap. M1001 samples at 48, so 44 content is upsampled, some claim to be able to hear distortion in very quiet passages possibly from the result of this upsampling.
The other problem with search is that you end up getting old information sometimes, especially if firmware has changed. For instance, that post mentions that the M1001 does not yet support WPA wireless security. It now does. I don't know if the M1000 is also able to be upgraded to support it or not.