i think trex products are really expensive!! but somehow davis gets them at very reasonable and affordable prices that defy the prices u get elsewhere, for example, proguitarshop.
i have not played a moller before, and i dont hear much abt trex effects. note the word "hear" hahaha.. it doesnt mean its not good though.
if ure looking for an overdrive with a boost u should check out the paul cochrane tim. its very very reasonably priced by mr cochrane but you've gotta wait. 2nd hand prices are obscene. buy them 2nd hand only if u're impatient and loaded.
voodoo labs sparkle drive is basically a tubescreamer with a cool blend feature. u get to blend in ur clean signal. its cool cos it retains some transparency. another effect that has that feature is the noc3 pure drive. pretty cool too.