Wow, I wrote such a long answer that Y!A trimmed it. Dang! Okay, I'm trying again.

I personally feel that the tube amp in question will sound better, but the Marshall will be closer to that tone you're looking for right away, right out of the box.

Below are three links, the first is Angus Young's road rig (or close enough). Gibson -> Marshall tube amp. Pretty simple.

The second is the tube amp I think you're talking about, and the third is the Marshall combo I'd go for if I had to. If you can't afford this Marshall combo, I wouldn't bother getting the cheaper one, I'd rather get the Crate.

The Crate will be louder (tubes always sound louder, a 5w tube amp is easily as loud as a 15-30 watt solid state), it has a bigger speaker so it will be able to voice your tone (especially the lower end crunch/thunk) a bit better, it will have more of the "feel" of what you're talking about and will in general sound better in my opinion, than any of the Marshall combos in your price range.

It won't necessarily have *that* tone out of the box, though, and that's the only reason why I would imagine why you would rather get the Marshall.

Marshall does offer some distortion pedals... check out the last link, perhaps this plus the tube amp would sound pretty good? I've used a Boss MetalZone with my Epiphone Valve Jr and it sounds pretty killer, I like the whole distortion pedal -> tube amp thing. Tube amps really sound good with stuff like chorus, phaser, delay, etc, that "sweetness" is really there with the clean stuff as well as the distortion.

In the end, the tube amp will be more versatile in having different tones (but needing pedals to do it) vs the Marshall that basically has *that* tone (which is truly a great classic sound, don't get me wrong) and won't really be able to go too much beyond it.

Oh yeah, and if you want a closer approximation of the AC/DC sound (or Slash from GNR for that matter) make sure you have a guitar with Alnico magnets in the humbucker.

EDIT: THanks for the kudos, Kabum, but I'm betting you read the answer before Y!A truncated it. =( God, it's so nice to have someone say such sweet things about me!!!

Hey, if you have any specific questions, email me through my profile, okay?

Saul