I prefer all of my high bias Stax phones with the SRM-717 (relative to the SRM-T1, SRM-1 MKII, SRM-212 portable). For the Lambdas the differences are marginal - including my little gem, the portable 212 -, for the O2 MKI / II, and the Sigma-202 they are crucial, for the 4070 significant.
Combinations with the 717 in order of preference (low bias phones with the T1):
1a) 4070
1b) O2 MK I
2a) O2 MK II
2b) HE 60
3) Lambda Signature
4a) Lambda Pro
4b) 303
4c) 404
4d) 202
5) Lambda Nova Signature
6) Sigma with 202 drivers
7) Sigma
8) SR-X MK III
9) SR-5
10) SR-40
Guess there are only mild surprises here. 
Edited by chi2 - 9/8/10 at 12:35pm