I've played around quite a bit with the NOS 6H30's and they do indeed sound noticeably different from the current production Sovtek 6H30. How much affect they have on the sound will depend upon the particular component they are used in. I would generalize and say that they sound richer in the midbass through the midrange and de-emphasize the highest treble and lowest reaches of the bass range a bit. They sound less sterile and thin but also a little less articulate than the Sovtek 6H30. I've used the NOS tubes in combination with the Sovteks to get the balance I want.
In the CD7 I would recommend not changing the power supply tubes, especially the two toward the back of the chassis because they are a closely matched pair. Pull the three power supply tubes and you will see that two of them have a matching color dot on them bottom. Leave those alone. I'd also probably leave the other supply tube alone too.
Conceptually it makes sense to leave the faster and tighter Sovtek tubes in power supply (non signal) locations and use the NOS tubes for signal. It also saves you a bundle of money.
In the CD7 I would recommend not changing the power supply tubes, especially the two toward the back of the chassis because they are a closely matched pair. Pull the three power supply tubes and you will see that two of them have a matching color dot on them bottom. Leave those alone. I'd also probably leave the other supply tube alone too.
Conceptually it makes sense to leave the faster and tighter Sovtek tubes in power supply (non signal) locations and use the NOS tubes for signal. It also saves you a bundle of money.