Thanks for the effort guys. I tried all the tweaks and got the Sony HWS-BTA2W to work *somehow* with the N800 OS 2008. It still had dropouts every 2-15 seconds without any other processes running.

I consider this way too bad for actual use though, so I'm still going to take my Sony audio gateway back to the store.

I'll keep my eyes on this topic though, so please inform of progress with the ALSA buffer and/or possible bluetooth DSP use to take stress of the CPU. I don't know much about Linux, but working with PC audio studio systems I know that the problem sounds a lot like the the CPU not being able to flush such a short buffer or that the size of the buffer is unpredictable.

(Setup used

N800 running OS 2008 (RX-34_2008SE_2.2007.50-2_PR_COMBINED_MR0_ARM.bin)
Kagu
Mplayer
Bluez