I tried that and it was much better but not enough to make a difference as compared to not in bridge mode.
I did notice a difference between a more modern platform and an older one - a huge difference. When running what I described in my first post (Dell Precision 490 with 2x Xeon x5060 or x5063 CPUs, DDR2 RAM and Intel Pro 1000 MT quad NICs) vs. a newer Dell T5500 with a single xeon w5580 CPU (same 4 physical cores + 4HT) and ddr3 RAM as well as PCIe Intel Pro 1000 PT quad NICs there was a noticable difference in the two (which seems obvious and logical since the W5580 CPU is worth more than the Dell P490 box all together).
There was still high CPU usage on both systems - not enough to make me want to go back to that bridge config.
I'm going to look for something that's passively cooled (like an Atom box) or something similar that I can use with some decent switches.
I really like these platforms I'm using but I'm quickly finding that the power consumption is making the hardware more expensive over the long run.