hi nick:
my DI is a behringer ULTRA D120.
i use that and go straight into my mixer channels XLR...
led: i suggest, like all my endlessly tinkering projects that you breadboard it up and tweak to taste, i was just seeing how little i could get away with.

gain: the gain was backed off on guitar IIRC..so theres a bit of room there.
500k: no particular reason i used that, ive tried 50k and its fine...very loud, too loud in fact compared to bypass , i'll probably end up sticking a taming resistor before the vol pot anyway..
edit: i remember now that i used 3 leds to raise the level, this was before i added the recovery stage,
edit 2: scrap the 1 led idea, it was too gatey even with the 1M in paralell....at least 2 leds were better.