I find that most djent guitar tones, even if they're played on a real amp sound a bit artificial (i.e. Bleed by Meshuggah), so amp modelling is kind of your friend for these sort of tones.
I know you said you don't have a POD but honestly, some of the best djent sounds come out of pod farm in my opinion. I haven't used amplitube in a long time, and I don't even know what sort of amps you get with AT3, but try a tube screamer pedal, a dual/triple rectifier amp model (if there is one) and rather than use amplitube's cabinet models use some quality IR's. I know you said you use redwirez, but some really good impulses that I like to use in djent stuff are the catharsis impluses (search on the sneap forum and you'll find them, free too).
Now I know it isn't much use since you don't have pod farm, but I'll share my settings for a djenty tone (maybe this will translate okay into amplitube too). I used pod farm, as well as some LePou plugins
Okay so the two main tracks will have the same settings really, just double track it and pan one left and one right. These two tracks are the loudest of all the guitars in this mix. first off put pod farm on and put a noise gate down. Adjust this to suit your guitar. Next I have the screamer (tube screamer pedal) Drive at 0, gain at 50% tone at 100%. Depending on your guitar you may want the tone somewhere else, but I sweeped it around and liked it on max. Next is the amp head, I used the Treadplate Dual (Mesa Dual Rectifier). Settings are as follows : Drive - 63%, Bass - 61%, Middle - 77%, Treble - 70%, Presence - 5% (I'll explain this soon). Turn off the cabinet. Next in the pod farm chain is the 4-band eq. All I've done is added 5dB at 1.4kHz. Last on Pod Farm is the digital delay pedal (not sure if that's in the standard version or FX junkie pack, I got FX junkie for free with mine). This isn't really for adding any delay, just thickens the sound a little. Settings are: Delay time - 20ms, feedback - 2%, low - 47%, high - 42%, mix - 17%. Now after Pod farm comes your cabinet impulse loader. The impulse is the "s-highpres" from the catharsis impulses. This is also the reason why there isn't any presence on the amp, this impulse already has high presence in it, but if you use a different impulse then obviously adjust presence to taste. In your impulse loader you obviously want 100% wet sound and 0% dry sound. After that I put in a parametric eq. Cut 110, 180 and 340 Hz a bit, put really steep narrow cuts at 770Hz and 10kHz. These EQ setting however may do absolutely nothing for your tone, as it's completely dependent on your guitar and your mix (as with all the settings in this guide really). After that I just threw a saturation plugin on. Two main guitars = done.
Next what I did was duplicate both guitars, and deleted pod farm. Again, both tracks have the same settings here, they're just two different takes. These ones were left mono and were about 12dB quieter than the other guitars. They're just there for some thickness. And because they're left mono you could just do one of them if you wanted, my tracks just had harmonies so I duplicated both. Anyway, put a gate plugin of some kind on first in the chain, follow this with the free Poulin LeGion amp sim. Put it on the green channel, mode set to lead, and settings are: drive - 1:00, Low - 12:00, mid - 2:30, high - 12:00, contour - 12:00, Presence - 11:00. Flip the high quality switch on the end. This was followed by the same impulse, same eq (which would probably benefit from a change, I was just too lazy to alter it) and same saturation plugin.
Last guitar track. I only did one, but you could do it twice if you want, however this one is 20dB lower in the mix so it's hardly there at all. You could honestly skip it and not really notice a difference. Anyway, I'll make it brief because this is starting to get long. Settings are essentially the same as the main amp, just I used the standard Treadplate instead of the dual model and used it's default pod farm cabinet rather than the impulse. This one also has the gain cranked on the screamer and has a compressor before the pod farm eq.
Finally, change the output of all of these guitars to a bus, filtered at 60Hz and 10kHz (again adjust to taste/your guitar/your mix) and put further slight cuts at 140hz and at 770 again. put an 11dB cut at 4kHz, which a lot of people say is the area where most amp sims sound crap. I tried cutting it out completely but it really hollowed out the guitar. -11dB was where I found it to be sounding good, also gave it a little bit more of a periphery kind of sound. All I did after this was put it through a pultec eq plugin and boosted 3k by a couple of dB, then into vintage warmer adding a little drive and finally the free ferric TDS adding slight saturation and slight emphasising of dynamics. I'm still on the fence about whether this is staying or going.
Anyway I hope someone gets some use out of that, took me a while to get that sound. Also, putting a bass guitar in your mix makes this tone infinitely better, and remember that ALL SETTINGS outlined here are a guide. You can copy them exactly if you want, however unless you have the exact same guitar and exact same mix as me, it isn't necessarily going to sound as great as I think this tone does (or for that matter, it might not even sound good at all). I might post a clip of this tone later tonight/tomorrow for all to hear.
Sorry about the essay guise, but hopefully someone finds it useful
EDIT: It also helps to make a send off that guitar bus to some reverb
