I have to say that you should buy the Banshee because on a low-end pc like a 166 a TNT card couldnt funktion probobly because the chip isnt fast enough.
I have p 200 and i have been advised to buy a Voodo2 and i did, and i works very good on my computer.
I have a P-200 MMX with 64 megs of ram that I recently installed a Creative Banshee 16 meg card into. It installed without a hitch and has functioned wonderfully since. I went with it over the TNT specifically because I have a lower end processor without an AGP slot. I definitely think the TNT is the better card if your CPU has the horsepower. On my system though I have absolutely no complaints about the Banshee.