Optimal sound configuration?
 

This is my computer:
Intel Celeron 1.7 Ghz
256 MB SDRAM
"S3 Graphics ProSavage DDR" graphics card
"Avance AC'97" sound card

I have some questions concerning sound emulation. I am now using WinUAE 0.822r5. These are the settings I generally use for sound:

Sound emulation: Enabled, 100% accurate
Frequency: 48000 Hz
Stereo mode: mono
Sound buffer size: 7 (1365ms)
Sound driver lag compensation: 0
Interpolation: RH

Now these are my questions:
1. Is there any good reason to use a frequency less than 48000Hz?
2. Is there any good reason to use a smaller sound buffer size?
3. When I emulate att 800x600 instead of 640x480 the sound gets worse. How come?