Is it common for tubes to outweigh the cost of the amp or preamp?

samiamnot-

No insult intended with my post. 

The intention was to raise awareness  that perhaps one might consider  starting with a substantial "box" before additional expense-especially if it exceeds the value of the actual box.

I use tubes in my system-amp,tuner and phono. Using NOS tubes that cost more than the equipment, won't ensure anything. Since it's a headphone amp, I would be more concerned using QUIET tubes. 

If you do find it improves your experience, that's all that matters. It's all subjective, YMMV and all that.

Considering tubes that cost more than the equipment, would be a reason to reevaluate my original purchase, and perhaps upgrade to a better unit.

VERY common .

That doesn't sound like a good investment. 

Changing tubes can have a positive effect on the sound or it may sound worse.  Or those expensive tubes might go microphonic in a month or few. 

I personally have found tube rolling in different devices to make relatively small differences in the sound signature, much like cables.  To me, it's worth doing, but in moderation.

I would have been inclined to buy a better amp than to have spent that much on tubes for a relatively inexpensive amp.

The difference when tube rolling isn't typically revelatory, which is what I would want expect if I spent as much as you did relative to the cost of the amp. 

I don't know what headphone amp you purchased, but even if it was used and you got a great deal on it, you shouldn't expect too much for what you spent. 

I hope you have an option to return the tubes.  My guess is you're going to be disappointed.

samiamnot

Power cables are something I'd only upgrade if I didn't know what else to upgrade and had excess money lying around. 

Okay, let me get this straight. So there's no misunderstanding. You are using the cheap stock factory power cords that come with your components????????????!

I would have stepped up to next model before investing in those CCa’s. Having said that, you did buy a very rare variant of 6922 tube. Those Siemens are excellent tubes and going to last you a very long time. 

If they don’t work out with current amp, hopefully you can use them with $1199 amp 😊