Well, true, there is many free and I mean totaly free of charge amp and cab simulators..
I mention boogex.. this plugin is made by voxengo..
Voxengo
next simulanalog guitar suite
SimulAnalog Guitar Suite
Amp simulator is a plug in that comes with Reaper..
REAPER | About
Studio Devil Virtual Guitar Amp Plugin Downloads (VST, AU, RTAS) Here you'll find FREE studio Devil... one of veeeerry fine amp simulators..
Ofcourse, fretted synth free amp
Fretted Synth
On this site you may look same simunalog guitar suite JCM800 but here you have skin for them
VST Tribute
There is another free of charge amp simulator...
Tubeamp download
Aaaaand aradaz amp simulatorS...
ARADAZ VST FREE
All of these amp&cab simulators are VST and therefore all will be working in ANY sequencer which support VST plugins...
How to ude them.. like any regular plug in.
Record something.. then open VST effect window, put some effects in it.. aaaaaand 'njoy
(I'm not much familiar with ACID, but I think you can manage and understand how it's going..)