IMO having a big knife is not even a question. I normally carry an ESEE 5, a Leatherman charge, and a Spyderco Military combo with me in the woods. I have no problem carrying all of those plus a Camelback with tp, a flint striker, an MRE, maps, tree painting cans, 3 rolls of flagging tape, etc. I also carry on my person a 100ft logger's tape, an aluminum clipboard, compass, GPS, and cell phone and cigs.
The first few days I was working, my back muscles were a little sore, but after 2 or 3 days, I was good to go.
That was all of my "essential" items for a day in the woods that would normally last 10-12hrs and I (70% of the time) would walk between 10 and 15 miles. I had to think about the "what-if" factor of me getting hurt or not making it back home that night.
I think that you definitely need a big, solid knife, a multitool, and a pocket knife for all of the random uses that a knife needs to be readily accessible.
Some other quality knife companies that I have used or seen are Swamprat, Zero Tolerance, the Gerber Gator, and Busee. I have also used SOG, Benchmade, Columbia River, and Gerber. The Spyderco Military, Zero Tolerance, and Benchmades were tha best out of that bunch. I have broken a few SOG and Columbia River knives over the years.
As far as a headlamp, Petzl makes some very nice ones, as well as CREE. You really get what you pay for with these.
Here are the links for some very good, bigger knives: Swamp Rat ESEE Busse Zero Tolerance
You might also start thinking for a camping axe or axe/shovel combo.
For knives, this is the best company that I have dealt with: http://www.knifeworks.com/
They are fairly local to BR and I normally get shite within a day or two. I get all of my Zero Tolerance and Spyderco knives from them.