If you're chopping down trees, splitting firewood, or doing anything else that involves turning big pieces of wood into smaller pieces of wood, get yourself a real axe or hatchet. I have a Gerber Sport Axe and it splits kindling like nobody's business. The Woodman's Pal, which I also own, was decidedly inferior at this task. It could be done, but it was frustrating, involved a lot more baton work.
If you're cleaning game, making spears, whittling, cutting soft materials, etc., get yourself a normal, fixed blade knife. I have a Cold Steel SRK and it's ideal; a Ka-Bar is good, too.
Ask Mr. Right Wing what Khukris are good for; I hear they're good at everything and he swears by them, but the only one I own is a piece of tourist shit and doesn't really do much well.
The Woodman's Pal is probably best suited to clearing brush. It can chop through small branches way better than a machete, and can tackle light brush in a way a hatchet cannot. You CAN split wood, carve spears, etc., with it, but there are better tools for those jobs.
I have no experience with the SPAX or the SP8, but typically my experiece has been that tools that try to do too many jobs well, end up doing all of them badly.
Exception: the Leatherman Wave can do many, many tasks very well. But you can't chop with it, nor should you use it as a hammer. So, multitool + hatchet?
Amen brother- A leatherman wave is an essential piece of kit.
Anyway, it looks like your looking for a heavy hitter. I live in Florida, so I'm dealing with brush clearing and softer wood most of the time. A full size machete is a great choice for that. For the harder wood, I highly recommend Estwing axes. Both are highly effective combat weapons. I imagine an axe would be more useful for an urban or northern enviornment.