I'm a Foobarist still rockin' the XP too.
AFAIK buffer settings are machine dependant. A smaller buffer speeds interface responsiveness and is preferable as long as everything can keep up so the buffer doesn't emply and stutter. But a bigger buffer shouldn't cause an audible difference, just increase the audio playback delay slightly along with the interface responsiveness. Buffer size becomes an issue when you were syncing to video (lipsync problems), or doing something like monitoring while recording tracks where the delay becomes a problem. For audio playback only a bigger buffer setting is pretty much a non-issue.
But correct me if there is something I'm overlooking.