I sometimes play with a Digitech BP355. I have no complaints, though I often play with nothing between my bass and my Ampeg SVT 4 Pro and Ampeg 8x10, besides the instrument cable and speaker cable.
I don't have an opinion about Boss, but I've noticed no degradation of my signal with my Digitech.
Here is a list of what I use. I will do my best to list things in the order they are run in my chain...
Sadowsky Standard 5
Sadowsky Modern 5 JJ
Korg DTR1000 rack tuner
Alesis 3630 compressor (first channel for bass signal, other channel for when I use my morley wah to tame the signal, but retain tone)
Ampeg SVT 4 Pro
Effects: on effects loop of Sansamp...also listed in order. I sometimes use my 50/50 button to blend the effects loop while maintaining some of the original signal.
MXR Bass Envelope Filter (I run this first to maintain proper filter dynamics)
MXR Phase 100
Morley ABY box (used to hard bypass Morley Power Wah Boost)
Morley Power Wah Boost (I did some work to make it sound beefier)
I feel that all of these pieces of equipment do a great job of retaining the overall sound of the bass, without robbing tone or loss/gain of signal.