As for the tube screamer...I've got one...it's a distortion stomp...I like it but seems to behave differently when used with different amps.
I simply hate the way it sounds with a transistor type amp (my practice unit) but when in front of my Mesa...oh baby! (neighbors come a knockin')...the over tones produced by the pedal when applied to a tube amp really comes alive...something a transitor amp can't do as well.
imho,
punkin