I'm going to go out on a limb and offer some good suggestions from my experience and my, personal and humble opinions of buying and carrying TKs for 10 years. However, there are much smarter people among us.
(I don't mean to sound like I'm treating you like a rookie! You DO have more than 500 posts. But you didn't give us much to go on, so I'm just going to ramble on because I don't know what your level of knife-knowledge is.)
First: I, personally, think that Benchmade gives you the best knife (possibly life-long) for your money. They're also darn good looking knives.
Second: Spyderco. They CAN (and often ARE) be considered ugly, but, no doubt, are functional. Spyderco has always put function before fashion.
Third: Emerson makes a darn good product, but I feel (as do some others) that they're over-priced. IMHO they're only marganially stronger than Benchmade and not quite as good in quality of craftsmanship. Their flagship, the Commander (a good TF knife) goes for $160 at online stores but a comparable Benchmade (Axis AFCK) goes for $120 at the online stores (you can get better deals on all on the forums). Given that perspective...
I never buy Emersons and always buy Benchmades.
HOWEVER, if you can get a deal on an Emerson on the forums (as you often can) for around $100 for a Commander or $80 for a Raven, Specwar, Mach-1, or any of the others then you definately ARE getting a good knife. I don't HATE Emerson, I just hate paying new-knife prices for them from dealers.
So in other words:
Benchmade first.
Spyderco second if you can stand the uglyness.
Emerson third if you can get a bargain ($80-$100) on the forums and don't mind a little "rough" craftsmanship for a really hard worker.
NOW, all the knives above are in the $100 range and will serve you well working them hard all the time for 5 years or more.
On the other hand, you don't have to spend $100
There are other supposedly "low-end" knives for under $50-$60.
In my opinion, the leader right now is Kershaw. The Ken Onion series is unbelievably cool and they're ALL darn good knives. Many people on these forums collect the Kershaw Onions. I have a couple myself. Kershaw makes a GREAT product for the price.
CRKT has always been popular and has been off and on as far as what you get for the money. Lately they've been ON and they have a WIDE array of knives that almost anyone can find something they like.
There's one more personal favorite I want to mention.
Timberline knives are under-rated.
Timberline has a line of two sizes of knives called the WORTAC that are an exceptional knife for the money and ALWAYS get good reviews. I have a large one and I'd never part with it.
Good luck. Let us know what you end up getting.