Quite different designs. As I stated on your other thread, some feedback about what you're after would be helpful. The main question is if this is for an acoustic guitar with a pickup or for an electric guitar. Assuming its an electric, there are characteristic distortions that most guitar amps strive for - unlike audio, distortion of certain types is desired in a guitar amp. Also, unless you're going for certain sounds, 100 watts RMS usually excessive for a guitar amp. If you insist on a "from the ground up" DIY design, I'd suggest maybe choosing a schematic of a moderate sized Fender or Marshall tube amplifier from the 50s - 60s and building that. I would recommend something between 12 and 50 watts. Good kits are available - check out the Ceriatone or Allen amps websites. Solid state designs are also available, but they are harder to make sound right for guitar.