Good topic. I'm currently on the hunt to upgrade/upsize my bass rig, and have gone through a number of them in the last 30 or so years, so here goes.
I'm currently using either a Genz-Benz M-200T (200w combo w single 12)or an Eden WTX260 (one of those 260W class D "mini" heads, about 6 lbs) with either 1 or 2 single 15" cabs loaded with EVM speakers. For bigger shows, I've been known to slave a 1,000W Crown amp and add another 15 or two.
I've always LOVED the sound of tube heads for bass, but it's not for everyone. I used a HiWatt Custom 50(!) for a long time with 2 of the single 15's. Not a ton of headroom, but WHAT A SOUND!
If I had unlimited funds (and a roadie) I'd be using the HiWatt 400 Bass rig with an 8x10 or 2.Listen to the Stranglers for a good idea of the p-bass/HiWatt combo.
I'm currently looking at a "vintage" SWR 400 and Goliath 4x10 as my upgraded rock rig. The aforementioned genz and Eden are just a little shy in the power department for some of my current gigs, and the outdoor fetival season is upon us.
Being a Canadian and all, I think I'd be on the hunt for a vintage Traynor rig, and the Genz-Benz would be my second choice. Not a lot of first hand experiance with Carvin amps (though I had one of the basses). Seems to be a lot of mixed opinions on the new stuff.
my 2cents!