Tube buffered CMOY ?

 
 
Hi. I was looking into various simple DIY headphone amps specifically for current hungry low impedance cans such as Grados or in my case 24 ohm Sony XB700. 
 
I came across the Apheared A47 amp and it looked interesting; nice and simple. However it got me thinking about building something similar except replacing the second opamp with a voltage unity-gain tube buffer in order to have a simple high-current hybrid amp.
 
Now I'm pretty new at this and could use a few pointers...such as which sorts of tubes should I be looking at, and why shouldn't I do this..etc?
 
Thanks
 
Here's the A47 info if you've not heard of it:
http://benfeist.com/a47/

Thats what the Bravo/Indeeds are over in the Desktop Amp section.
You can pick one up cheap on Ebay.

What you are describing has (sort of) been done with the audiovalve RKV headphone amp. its not a CHA-47 pseudobuffer configuration, but a tube buffered opamp. 
 
Between their patent documents and info you can find on the web you should be able to find enough information to just buy one to save yourself the headache of figuring out "what they didnt put in the patent" you know, the last little part that will have you scratching your head while your amp emits expensive smoke....

How about looking at a class AB tube buffer section, driven by an opamp?
 
This makes for some good AB reading
 
http://gilmore2.chem.northwestern.edu/ubb/showpage.php?fnum=3&tid=5340