5 watts from the micro cube bass? You cannot be serious! At £200 that's £40 per watt.

The Briefcase will give you 100 watts for about £550 - a far better watt/£ ratio.

The Line 6 is not a bass amp and also very underpowered. Its strength is teh huge range of FX - mostly not needed for bass.

Cube Street also not a bass amp. Cube 60 comes in a bass variant, but no battery option.

Ashdowns lovely and I particularly like the blend that lets you add a tone an octave down from each played note. To get the full benefit of that you'd need teh 15 inch version - but not battery powered (well, 300 watts would flatten a battery PDQ).   I still think I prefer the Hartkes though (but also not battery).

If you can get a second hand crate Taxi TX 30 or TX50 in the UK (imports from the USA are likely to be prohibitive) it might be worth a go. A burglar alarm will provide a backup battery but the parts off the PCB are VERY hard to get - I spent 6 months chivvying the makers for a gain pot, which is after all a wear part.

Most pignose stuff is good. But for bass you need a big one.