I really like Kuechly but he's had 3 and a half really good seasons in the past 15 years... He's there with Bowman and Von Miller for me, Elite currently but haven't played long enough.
Mine are Ray, Urlacher (that tampa 2 was just so good with him), Brooks, Ware, and Patrick Willis.
I love Seau but not as a LB of the 2001-2015 years. I'd take Zach Miller who was in his prime to late prime over Seau. Not for a career of course, but since 2001.
Guys like Fletcher, Keith Brooking, Takeo Spikes, James Farrior and Karlos Dansby would be close for me, all were huge impact guys while not as flashy as some.