A little late to the party...
I'm loving the Soldano 100 clean channel with my 6 string Ibanez (a GVB36, not the SRC6 :p), and the XXL V30 cab with the 409.
It's like the bass rig we didn't even know we had :)
I can get thick and powerful lows, punchy middle, a nice shimmering high end... I like it tons better than the flip top and 1x15 Line 6 so graciously gave us... >.> :lol: I haven't even messed with adding EQs, compression, or tweaking amp/cab settings, yet.
I also have a Zoom MS-100BT, which has some of the bass models as the B3 mentioned. I like them, but they take some tweaking to get the best out of them, so if you don't mind that (I don't), they're useful, too, and the bass effects are definitely better suited in one ways. I don't use it for amps, now, just to simplify things and liking the 'SOLO 100 CLEAN' better o.O
An advantage of using a 500X is the A/B paths; if your bassist likes some overdrive/distortion, you leave one side clean to retain the low end :)