Manley Stingray II

Have Siemens ECC81,Siemens 801s,Mullard CV4024 and the stock Electro Harmonix ECC81 tubes.LOVE the Siemens ECC81 tubes.Cardas GR sp cable and Merlin VSM-MXr/MasterBAM.
What other pre tubes can I try that works well in the Manley and that may beat the Siemens tubes ?
German telefunken E 80 CC can be a good option. i am using them since 6 months or so without any problems. The originally supplied from Manley  ECC81 were not so good (giving sometimes noise and are unstable).  As to power section, I am using a very good substitution for EL84 - soviet 6P14P tubes.