Why certain games that i played like chrono cross and digimon world, i get lousy sound? but when i tried other plugin like epsxe SPU it works fine but has a lower sound quality than Null2 SPU because i rate it 44kHz 16bit.
Well with Chrono Cross you'll probably get mdec lock-ups with null2's so I would recommend switching over to Iori's for that game. As for the other game, I haven't played it so can't comment. Play around with your buffer settings.
The best config depends on your computer. I use the following:
Sound Buffer: 7
XA Buffer: 42
High Resolution mode: ON
Wait for XA buffer is free: ON
Show realtime config window: OFF
Enable Noise and Pitch Modulation: ON
Enable Reverb: ON
Enable SPU IRQ: ON(off in epsxe's main sound config)
Enable Compressor: ON