Bass POD.   Great compressor,   overdrive effects,  easy to use.    The SVT,  Eden,  Gallien-Kruger,  and Acoustic 360 emulations are excellent-  there are 15 amp models and one preamp model.   Some of the effects are good like the octave,  phase shifter,  and Big Muff distortion.  $350.  The Bass POD is one of the best investments I've ever made in my studio.
   SansAmp Bass DI.   $180.   It's highly regarded for a DI device.   They also have a version called the Bass RBI that is in rackmount form and it has more EQ control,  $300.