So after quite a bit of research I settled on the SOHA II headphone amp which utilizes a vacuum tube input stage and solid state output stage. All of the info including schematics and building instructions can be found here at http://www.cavalliaudio.com/ and PC boards can be purchased from http://www.glassjaraudio.com.
This is a pretty clever little design utilizing inexpensive and easy to find 12au7 preamp tubes, the schematic is shown below (this is the schematic for one channel). The beauty of this design is that these tubes only require 60-90 volts to run properly as opposed most tubes requiring 200+ volts to work so it is much safer for a first time builder such as myself.
Here is the power supply schematic as well:
While the schematic looks pretty complex at first look it is really quite an elegant design making use of relatively inexpensive parts and is a rather robust design allowing for easy tube swapping.
Once I did all of my homework I ordered up most of the parts including the circuit boards from http://www.glassjaraudio.com and purchased in the rest from Mouser, Digikey, and some scraps I was able to scrounge up at work.
Step 1: Design the Amplifier Housing
I started out with plans to use a commercially available metal enclosure but I decided something a little more unique would be more interesting. So I sketched up a little design:
Then a quick CAD model - Google Sketch is very cool!
Step 2: Build up the Circuit Board
From a box of parts to the nearly completed board
Step 3: Build the case and and put it all together
The corners and top piece are Bocote while the main body of the amp is Zebrawood
I put LEDs under the tubes to get them to glow
Now that I have had this for a while I find this amp is quite incredible, its almost like switching to a high def TV from std def. The bass has a lot more punch, the midrange/vocals are amazingly smooth and the highs shimmer and are exceptionally clean. Another observation is that the music takes on an almost 3D quality. With such clarity your ear can roam to single out individual instruments in a way that I had never experienced before. Bottom line - I love this little amp!
I'm thinking maybe this coming winter I may just have to try another one of these!