I ran this combo with some 480's and schoeps last spring and did some
comparisons at shows and in some small bars. Every time the m148>V3
combo was more direct sounding than the straight V3(like Trey said) it
just brings the music closer. Actually what I think it does is the M148 doesn't pick up as many reverberant noise reflections from a room
(esp. in a bar) as the straight V3 with 25-35db of gain. The V3 is so
producive of what you hear it picks up alot of the "room". The m148 seems to tame this since most of your gain (-20db) is derived from it.
The lowest gain setting on the V3 is sometimes still too hot, but don't worry if you see overs b/c you will never clip it running it so low,believe me. You will have waveforms that cut, so you will lose some dynamics, (but I doubt you would ever hear it) so if your anal about waveforms beware. I loved the combo with both AKG omni's and mk21's the best.
happy gearing,
callery