I could be a dick and yell at you for being a pirate, but we all have to start somewhere, and I sure as hell found it easier to progress quicker with better plugins.
Now, on topic:
For big guitars, or big anything, it seems like the key is not to process stuff too much.
Work on getting great raw recordings and the mixing process is that much easier because of it.
I heard it a million times and never took it on board until recently. But 15 extra minutes of yelling at your guitar cab and your SM57 is definately better than 3 hours of eq'ing guitars to sound decent raw before you even try and make them work in the mix.
If you lack a good guitar amp. Like if you have an MG or a Line 6 Spider or something that, one way or another, sounds like your dead hamster could have shit out, then go for something in the vst amp modelling domain.
There's SoloC, Wagner, Dirthead, 7170... Then there's Revalver, which sounds utterly fantastic, and there's many a person on this forum that gets away with using just the demo, myself included, as the hiss isn't really audible in a dense metal mix. It gives you time to do some mixes with it and make money to pay for it or whatever.
Personally, I found it much harder micing a real cab with a real mic and a real amp, but I'm all the more inspired to go back and start micing cabs again now that I've done some mixes using Revalver.
Revalver to me is like Windows Vs Linux.
This analogy will probs suck a bit, but hear me out.
Revalver is kinda, a simplified version that 90% of people can use that can still wield fucking FANTASTIC results, it's just a bit easier to coax workable results out of it in the first place, but it's potential is ultimately a bit limited.
Real amps, through real cabs, miced up with real mics going into real pres is your Linux, harder to get into, even harder to get good results from, but the sky is the limit.
Starting with Windows may want to make you move up to Linux, just maybe.
Although, 90% of Linux's userbase seem to be pretty fucking up themselves because "OMG GUYS LINUX OWNZ EVERYTHING ELSE OMGAWD!" but that's besides the fucking point! Haa.
Anyway, second, for teh BIG GUITAR TONEZ, mix bass guitar higher then you may think, and take some bass out of the guitar.