My personal preference is for cab.s that are very accurate - i.e. are designed to have as flat a frequency response curve as possible, rather than imposing a particular sound. Its much easier to add colour rather than take it away.
In all the brands that we carry - or that I have heard - I think Acme and Accugroove are the most accurate.
As you already have a big rig - and often play at ridiculously low volumes - I strongly suggest that you check out the Acme B1 (31lbs) or Accugroove Tri110 (29lbs) or Tri112 (38lbs).
These are seriously good speakers for the size and weight. All are three way systems with separate woofer, mid and tweeter.
The Acme is -3dB at 40Hz and -6dB at 30Hz - that's seriously good low B performance.
The Accugrooves don't have quite the low end slam of the Acmes, but slightly smoother mids and highs.
Now I know you asked for a combo - but the cab will have a huge impact on the sound and its most important to get that right first.
Accugroove have just released a light weight amplifier, which I haven't checked out yet. It will be available in a combo version of the Tri112 (47lbs), which would be worth looking at.
Alternatively, if you want a pretty transparent sound, check out Acoustic Image heads (5lbs). Otherwise there are any number of lightweight heads - Markbass, Eden, GK all have heads around or under 10lbs.