Tung, i'll post your email comments (for anyone following this thread):

Looking at the schematic, it looks a lot like the VC-508. The V5 isprobably an update of the older amp with a larger speaker and someupgraded parts values. Do you want more bass in the clean sound or distorted sound? You couldbump up C1 to 22uF/50v, but it might make the amp sound flubby/farty. Other areas to look at would be replacing the speaker with a better oneand replacing the output transformer with a better one.

To me, cleans sound ok... i'm using humbuckers so messing with the tone knob on my guitar get's me some good tones on it.
While overdriven the amps sounds ice-picking thin, i use a multieffect pedal, Digitech RP250 and all my distortion based presets sound like that to (not thru my Vox Pathfinder 15R).

The speaker replacement issue is a bit confusing... the only spare speaker i could use is the 8" stock one on my Vox 15R and as a said erlier on this thread, lots of reviews claim that swapping the speakers and tubes helped, and others claimed it didn't... so, i'll try using the smaller speaker i have at hand (not a big step forward, but might help).

As for the OT, same issue... i had to buy one.

At first i thought i could get decent tones just by replacing resistrors and such (an inexpensive and fun way of modding) rather than swapping parts (no fun-labor factor there, and could be a bit expensive)... but i guess that drill goes: first swap stuff then mess with the board.

any recomendations on an inexpensive OT?... theres a lot of space in the cab.