Ken,
If you're considering the B&W N804, I'd strongly recommend reconsidering the N805 with a REL Strata III. About the same price with much better performance (IMHO).
Although I've never heard a pair, I'm really interested in what the Green Mountain Callisto would have to offer. However, do as much auditioning as possible before spending a time. Recommendations are only a starting point.
If you're considering the B&W N804, I'd strongly recommend reconsidering the N805 with a REL Strata III. About the same price with much better performance (IMHO).
Although I've never heard a pair, I'm really interested in what the Green Mountain Callisto would have to offer. However, do as much auditioning as possible before spending a time. Recommendations are only a starting point.