I haven’t tried the GF(I don’t see a GF in Devi’s line up, there are the DF, VF, KF and GZ.), but I do have an older DB (from the E-13 days).
The DB will add a lot of low end. Mainly it boosts the bass and rolls off the highs.
It’s also quiet when in use. Mine works best after other pedals and won’t work in front of some (db loss if in front of some pedals, impedance or buffering?).
If big and dark is your thing get it.
Both the KP and TP sound very good with bass, and are probably the most controllable pedals in the line up.
The 33 isn’t bad but looses some of the lows, sounds fantastic when followed by a DB though.
If over the top and out of control are your thing the DF, SM and especially the AE (most noisy pedal on the planet) get there like nothing else.
Any way, defiantly get the DB. At $55.00 if it’s in the budget also get both. It will still be less than most single fuzz pedals.
BTW over on the Devi boards there are sound clips, a forum and people will swap AR pedals back and forth so you could probably swap it to some one else later if it’s not for you.
http://www.deviever.com/
MM