Hey dude.
First off you've got great taste in shooters
Secondly great to see there are other ballers in slough woop!
Out of the three guns you've chosen I'd basically say if you have the dollar go for the Dm9. They are the lightest and smallest matrixes to date while still packing more features an innovation than ever.
Heres the man TommyG, who made this vid just for you to explain in further details the advantages of the Dm9
[youtube]03wMXldJ-qg[/youtube]
However if you're on a bit of a budget check out this Camo PM8
http://slothball.com/viewprod.php?displayprod=1518
Still an awesome shooter and in a fancy anno scheme too, ideal for the baller on a bit more of a budget.
As for the 08 detent system, I ran a DM8 for the majority of last season and never had any issues with my eyepipe or detents. However some guys on the team did manage to spin their magnets around which proved to be a nightmare to sort out. The 09 system is just a great example of Dye reacting to player feedback.
which ever gun you decide to go with I'm sure it'll serve you well
Jack