I love its nakedness

Comparing it to my clothed 940BE @ 3.8GHz, 1.43V, allowing for 19C ambient, my 2x pa120.3 set up, more powerful pump, temperature controlled fans, no C&C and recalling the numbers from memory ( ) I'd say your temps look about right ( ). You may gain an extra 1 or 2C at load with something like the HK 3 I use.

One thing that would worry me would be the convex nature of the base on some blocks, I'm unsure how the naked cpu die would cope with the localised pressure as the block was tightened down.

Other than that, you could add more/faster fans and/or another rad. With 2 x pa120.3 + 6 YL @ 800 rpm my water load-idle is seldom more than 1.5C, this should give you another 3C, maybe slightly more, at the cpu.

For reference:
Amb: 19C, cpu idle 25C, cpu load 36C, water idle 21C, water load 23.5C