People really need to stop saying "VST"'s, because they're not being clear about whether they're talking about synths or samplers.
Can you get it done with a VST? Yes, two. One is called Kontakt (a sampler, not a synth), which you have to buy to get access to buy Shreddage. The other is an amp sim of your choice. I recommend downloading the TH2 Overloud demo. Good stuff. Shreddage includes low Bb tuning, and Shreddage X (the lovely $20 expansion that's bigger than the original) has Ab tuning. That's all of the low dark metal tuning you need right there. Of course if you can't afford Kontakt, zircon is working on bringing Shreddage to DirectWave.
Can you get it done with a synthesizer? If you feel like spending years fine tuning your replication of a human playing rhythm guitar, sure. (in other words, don't do it. Especially not with something like sytrus and hardcore. Sytrus is pretty powerful but it's not meant for physical modeling. Hardcore sucks hardcore.)