Have you done an analysis to estimate how much more money you'd make with a better performing body?
If I were coming to Vegas anytime soon, I'd gladly let you use my d300 and d700, in exchange for getting me into a good MMA fight to shoot with you, like a Uriah Faber fight.
Honestly, if I were you I'd look into getting a used d300 for cheap. It might pay for itself in a few fights and then allow you to set aside more money for a d700. At ringside, the d700 would rule. In the cheap, nosebleed seats, the d300 should do very well.
Here is a comparison if you want to pixel peep. D200 ISO 1600 1/8sec f/5.6 and D300 ISO 3200 1/10sec at f/5.6. I exposed the d200 shot brighter than the d300 deliberately. You can see that the patches look very similar, which means that you could shoot at or near ISO 3200 and get similar results to what you're getting now with the d200 at ISO 1600.
