I second Boom's ashdown recommendation. I was really partial to this MAG300 I had for a while. It sounded really nice. Built like a tank, I am sure the combo version is great. All their stuff is great. SWRs really do sound amazing, or they sued to, but I experienced reliability issues with every one I've ever encountered. H aven't touched one since like 2006. Never again.
I also agree that the Markbass stuff is great, even the recent affordable stuff sounds pretty good.
Be sure to try out all these new, Ultra-ompact/light class D heads. I'm telling you, class D technology is really great for bass because of how it handles transients and also its whole methodology is fatastic ebcause it doesn't need buulky ehat sincs or anything. It doesn't get hot at all... Class D is where its at on paper.... in rpactice? Every time I try a class D bass amp I like it. They don't sound like an SVT if that's what you're looking for but they provide loud, honest bass for days. I like d the TC amp a lot, but I am a long-time TC guy so I'm biased. If you're not getting a tube amp then i would be trying all these tiny bass heads at a store before I looked at any old fashioned solid state heads like Ashdown, SWR, etc etc. I know Markbass makes class D stuff, haven't tried them though. I'm telling you,, this class D thing is the future of solid state amplification. Unless you're going to pony up for an old tube amp I would really be looking at class D. I eman, you cna fit this shit in a backpack and borrow a cab at the gg, dude!
another great solution is a used line6 bass pod (even an HD can be had for peanuts). The classic tube bass amps they mdeolled, aprticularly the SVT? sound pretty decent and you get all those goofy effects too... if you disable the cab and use it with a really clean pwoer amp ito a typical bass cab like a 4x10 youwill be surprised how good it sounds. And these days you could get a class D pedalbaord amp. I had a friend who did a rack with a bass pod and a crown and that rig soudned great but these days you could just use the floor version or the kidney-shaped little pod with a 3 or 400 watt pedalbaord amp and be able to walk to the gig with that in your backpack assuming there's a bass cabinet there. I'm telling you, I was shocked at how nice the bass pod soudned the first time I ehard this guy use it at a gig. He ahd stage volume and sent a direct signal to the PA and the whole thing was just great. it didn't look impressive like a raging SVT, but it was low hassle.... now with iny power amps thata re the size of a a big muff NYC? Its a really nice solution that will give you simualtions of soem classic old school abss tones, a bunch of effects and can travel on th subway with you. And of course you can also get a cab or yourself too, the whole rig will be cheap enough that you can go find a used 2x10 or whatever type of cab you like. Personally? For mdoern bass I like 2x10s with an 18" or 4x10s with a 15". For trashy rock I always played through a straight marshall cabient loaded with bass cone celestions or JBLs... I really dislike cabs with horns, but I dn't like to play slap bass and when i do I am shooting for a really 70s sound like ons telly dan's Peg, not something bright and in your face with pingy pops.