For those returning to this, it looks a few things could be the culprit. The biggest issue being the latest graphics driver (including the one just released Monday or Tuesday) causing odd frames per second. After rolling back to I think it was one of the 355s, disabling Core Parking (searching the register for "core park" and setting any keys with valuemin/valuemax to 0), ensuring the power profile is set to full power, and making changes in the NVIDIA control panel (setting the global setting for power management to Prefer maximum performance, and setting Arena's individual settings: threaded optimization off, triple buffering off, and vertical sync off). A few of these settings, particularly the NVIDIA control panel settings, may not be needed. Now we start out with almost 150 FPS.