All three re exctly list I woiuld make and yes if you want to ever push it 50 watts could be a problem.At 50 wats you would want a full tube do distortion was 2nd order and not nasty.Unison SE is 140 watts.And when you want you could have Parts Connection soup it up for you (read review at 6moons on level 3 uipgrade.Read article rcently that made upgrading make more sense.A company will use parts and need a 5 to 1 return on part thus all but most rediculously priced gear will use best parts like Hovalnd or Black Gate Caps,Vishay resistors etc.But when modifying you pay for part and labor.You save buy buying modded goods (in your budget) from dealers here on Audiogon like Underwoodwally from the get go but buying stock allows youy to split cost and have fun of geting amp improved after you've had it awhile.Jolida and Unison are both companies with a number of moddifiers though Pathos (*which is beautifull BTW) I have not seen offerings for mods.
G'luck
Chazzbo
G'luck
Chazzbo