To the op, all of the knives you listed are good to go. No matter which one you choose, it's a good choice. With that said, only you can figure out which one is the best choice for you based on your needs and wants, what you'll do with it etc. Best thing to do is ask yourself what it will be used for. Look at your routine and narrow it down by use.
Here is my personal short synopsis for each knife, I have only used the PM2 and 551, so take the rest with a grain of salt.
Spyderco; known for great ergonomics and slicey FFG blades. Not necessarily great if you will use them really hard. Better off as knives, not an impromptu do all tool at the construction site.
Benchmade; Really fun knives with great actions because of the AXIS lock. They run a little beefier than Spyderco knives, but sacrifice cutting ability.
Manix 2; Is known for outstanding ergonomics that can be used for long periods of time in comfort. It also has a nice blade that will make short work of what you're cutting. Downsize is that it is a pocket hog, not in weight but in size. It has a ball bearing lock which is similar to the AXIS lock. Good for if you use your knife a lot.
BM Freek; Very similar to the 551, but with S30V and a higher grind. Ergonomics look a little better IMO. I would choose it over the Grip.
BM 551; A very tough knife that will serve you well. They have good ergonomics and a whole lot of jimping and texturing so you won't lose a grip on it, hence Griptilian. Not the best slicers but they cut.
PM2; One of the most popular Spyderco knives. Very light, great ergonomics, a thick stock blade that can still slice, however it has a fragile tip. It has the compression lock which is easy to manipulate and keeps your fingers out of the blade path.
BM 580; Is assisted opening, so unless you want AO I don't see a reason to consider it over the other knives.
The PM2 gets my vote, but that's just my opinion. Like I said earlier, only you can decide what is best for you.