Recently, dangling a modest expense account and a yen toward completeness, we tried to round up companions to accompany us to some of the metro area's finest second-tier sushi establishments. No one would go. Second-rate sushi? They'd rather pay for their own topflight sushi than eat the second-best for free. And our friends are notoriously cheap! Reader, we were forced to have second-tier sushi alone, and we don't recommend you repeat the experience. But that's the very essence of the matter: Scrupulously fresh tuna is a delight to the tongue and a jewel to the eye; old tuna is cat food.