I own the DM Pro kit. I would imagine the DM5 is something between D4 and DM Pro. Sounds and samples may be the same through all three brains, processing as well, but the tweakability of each sample sound, parameter adjustment, combination of different samples to create your own snare or cymbals or whatever, is quite extensive on the DM Pro...more than I actually use, but I do use some. I would imagine by what I have read that the DM5 is somewhat like this, perhaps less detailed on the parameters that can be edited and the level of editing detail in general.
Scrubucket, if you're wondering what kind of sounds I get out of the DM Pro to tape, likely similar to what you could expect to get out of D4 or DM5, go to soundclick.com and search Dale O'Brien. When you pull up my page, download and play "Wild-Eyed Jim's". There are other songs on my site from a previous band of mine on there too...THESE DO NOT USE THE ALESIS, only Wild-Eyed Jim's. I think I got a rather believable sound out of the thing. Anyway, it will give you a rough idea of what you can expect from an Alesis-controlled electronic kit.