Looks like I narrowed the wish list down to a mountain bike with trapezoidal frame, full front and rear suspension, gel seat. Not concerned about the weight or about having more than one gearshift range. If possible, would prefer taller handlebar position for more upright riding.
Looking for specific model recommendations, ideally under $5K fully configured. Less would be just fine. The main goal is getting exercise in reasonable comfort and without getting too bored.