Hi!
After unsuccessful attempt to build 2.5.70 kernel I applied preemptive kernel patch on 2.4.20
http://www.kernel.org/pub/linux/kernel/people/rml/preempt-kernel/v2.4/
The improvement is noticeable. XMMS runs smoothly even when running Mozilla ( yes Mozilla is sort of benchmark for me :) ) I've compiled my soundcard module into the Kernel.
Those who cannot wait for preemptive feature but are finding it difficult to make 2.5.70 work should certainly check this out.
System Config:
Cyrix MII 233 MHz 64 MB RAM CMI 8738 PCI Sound Card
bzImage size = 724K