You'll definitely want the Marshall sims. I used to be able to get a really good AC/DC rhtyhm tone out of a (real) JCM 800 but I guess that's more the Bon Era guitar tone. Still their tone hasn't changed THAT much. It just got fatter/thicker and that's more likley due to more quality production.
In TH2 I've been able to get those types of tones pretty easily but I didn't full on try to dial it in because it's not much use for my current work which is more high gain. I'd say if you are going for Malcom you're definitely gonna want to double your rhythm tracks (as in record it twice as accurately as possible so practice up) then poke around any Marshall presets to see what comes close... then study the preset, SCRAP IT and rebuild it starting with just the head and cabinet. I find a lot of those presets are okay for getting ideas on how to build up a sound but inevitable they never quite fit right the way you want in a mix and tweaking them just screws everything up.
Since you are going for such a simple tone just using the right head and cab sim will get you a long way. Then really spend some time working with whatever room and mic settings the sim has to get it sounding "live" (and by live I don't mean on stage... I mean like a proper sound room, closet, whatever). TH2 does this very well (the full version has a ton more stuff than the Sonar version) but any good sim will have similar options and I've hear that IK stuff is pretty quality. Even Guitar Rig can be coaxed into a passable Marshall tone if you are will to put in some effort but I find their "room" setting to be kind of limited.
Also I've been having REALLY good success using my amps line outs with sims instead of plugging straight into the interface. I go from the amp to my mixer and then into my interface so I can keep the signals under control and even do some light EQing on input. The most valuable part of this method though is you are plugging into a proper guitar preamp which most interface's Hi-Z/Inst inputs simply cannot compete with (even if they claim they do).
Still you aren't going to get the exact sound of a cranked and glowing 100w head going into a 4x12 cab in a nice room with nice mics but really... who aside from dudes in actual studios or who own their own house can really get away with that kind of mayhem.
Cheers.