Huh?
Are you chaining two amps together or asking if people run more than one amp?
Don't chain two amps together. Among other things, you dramatically increase distortion and might overload the input of a second amp.
For me, the point of an amp is to have as few components as possible. The more devices in the chain, the more the signal is altered.
One amp I'm working on (and I willfinish it one of these days) just has an attenuator, one tube per channel, one resistor, one capacitor, and one output transformer. It's the most stripped-down design I could find, so I've dropped a little north of $1k into the best quality parts I could find.
If neither of your amps cuts it with your headphones, it's probably time to sell them and buy a capable amp.