your talking the tech 21 bass stuff? I love the RBI preamp, I've tried the landmark 300 (into 4ohms) and have heard someone play the 410 bass cab in a store, and I bought and tried the landmark 60 bass combo.
Quick synopsis:
RBI preamp: great flexibility, inexpensive for tone, can improve the sound of almost any rig or guitar. I use to use mine as a preamp bypass for my swr bass 350 head that I owned, now I have a stewart amp (see sig)
Landmark 300: good tone, might be underpowered for some cabs, heavy in my opinion
here is a post of my review
410 bass cab: A friend from TB (Fishbulb) works at a music store and he played and compared the 410 tech21 with and eden 410xst and the tech 21 sounded better to me overall, it does have lower wattage rating than eden however, even though the tech 21 has no tweeter the upper mids seemed to come through quite well, harmonics etcetera.
I recommend people look into trying one if they can.
landmark 60 combo (with the 12" speaker) I bought and tried the LM60 combo and was not happy with the volume, tone. with just the one 12" and 60w it was not loud enough or deep enough for my loud church gig. we generally have stage volumes about 100 dBc and it got lost pretty quickly. the LM60 has a RBI built in, but the speaker or box design left the unit sounding "boxy" or honky to me. I hate resonances and boomyness.
hope that helps
BTW I also recommend some of their Guitar pedals and combos for six string guitar. I actually own a TM60 two channel 60w amp. I think it sounds great, not tube great, but rich sound for solid state, very flexible. the GT2 pedal is great as are some of the other tech21 stuff hear some samples
At the TECH21 website