Since i unfortunately have to live in the REAL world and I'm my own roadie my main concern is size and weight so my dream rig is what i currently have, A Markbass CMD102P combo amp. Sounds good, cuts good as a stage fill amp (I always run into the front end sound system to fill the house) it's small and only weights 44 lbs.
MY ultimate rig would be one i use to own, an Ampeg Pro5 head bridged to push 1350WTS at 4 ohms into an ampeg 4X10 4 ohm cab. Filled any stage with high volume high HEADROOM bass sound, it was louder than any amp i ever played through before or since but sounded like it wasn't even working up a sweat. NEVER farted, NEVER overloaded, it was pure thunder. Problem was it weighted a ton, it killed me to move it, and sound men and the guitarists in my band hated it because I was way to loud on stage. (and i was!;-) I could drown out Marshall amps if I wanted too. ... But it was major over kill to play local night clubs and bars. It would have been awesome in concert halls and huge stages though.