At first. The unit is able to drive 600Ohm as you stated but read the text below and look at the PGA4311 as a opamp the same time.
Taken from Walt Jungs article on buffers for audio :
"These first two installments on high-performance audio with ICs and discretes have focused on choosing (or designing) a buffer stage for best overall performance. In IC op amps with poor thermal design, heavy output load ing can cause shifts in effective input offset, as well as associated linearity changes. These load-dependent shifts can be identified with testing, allowing easier device selection to minimize this problem.
However, simply buffering the amplifier's output with an isolated-package circuit removes this source of error, and maximizes op-amp linearity. This step is recommended wherever it's practical and needed. Buffer circuits can be chosen from a number of ICs expressly designed for such tasks, as was noted last month. Or, they can be designed to match a given set of conditions, as in this example.
With short cables and a light load there is no need for buffers.
"How are you gonna set the damm thing to a certain attenuation... I think the interface in quite impracticle...or are you going to use your PC poort for that.. then try the evaluation board.."
With your words : The interface is damm easy!
You just have to feed it from some micro (Read PIC,AVR,8051 etc..)
The interface is called a SPI interface and there is many applicationnotes on this.
I am going to use a AVR to control it. They can turn the oscillator off. I think i am going plan a project this weekend on this and drop the WM8816. It is a lot easier to get the PGA4311.
I was really looking forward to your implementation based on the Wolfson circut. Able to use the op amp (or any inverting amp) of your choice and not constrained by the quality of the internal opamp. I was all a'twitter with anticipation.