There are a few things you can try. First off when you’re using LeCab with some good IRs you’re going to get a whole lot more usage out of the Cubase AmpSim plugin, it’s actually really cool when you run it through some better IRs, but he Poulin plugins are awesome and will work just fine.
For good basic “metal” guitar tone you should keep a few general concepts in mind (emphasis on basic):
Double track rhythm parts and pan them left+right
Stick to 2 tracks, if you overdub any more than that you’ll get muddy crap tone
Use less gain than you think you’ll need, most of the heaviest rhythm guitar sounds are relatively medium gain
Less is more
Make sure your parts are clean, if you cant play it flawlessly at 1.25x speed then it’s might above your ability for clean recording
Don’t scoop out the mids
Those are just basic things you can do to get within the ballpark. The more you add to heavy guitars the worse they sound, you really need to keep it simple. Typically what I find is that bass knobs on amps (and amp VSTs) tend to get too muddy, so I roll most of that off usually and then add it back in with a post EQ. And while on that topic you should get real familiar with low end frequency management (for guitars as well for general mixing). Use high pass filters carefully to clean up low end rumble and to gently ease some bassiness out of your guitars so the kick and bass guitar can be clearer.