You’re never going to get the high string to sound as fat as the lows unless you bi-amp and eq each amp different. Plug your guitar into an ABY BOX. Dial out the hi’s on one amp and boost the hi’s on the other. You might need to add a (50ms) millisecond delay with the shortest repeat possible. Crank the balance knob on the delay pedal. You may need to add a chorus pedal with subtlety so that it sounds 3d and not warbly for a more realistic 2 man guitar effect. The chorus on one amp also will tame the lows a little bit so it isn’t so woofy sounding yet punchy glossy . And you can move the treble knob on your amp until you find the sweet spot you like. -You’re welcome.
Some great IR's by Redwirez are available for free at their website as some kind of 25th anniversary thing, and if you use windows you can use VSThost as your "DAW" although all it does is host plugins. It's great because it loads so much quicker than a full DAW and doesn't have all the tricky options that just distract you from playing guitar. Like a real amp, it's plug-n-play (after setting it up, of course--- you'll want to set the sample rate to 192khz so that you can get ~8000 samples a sec with oversampling at 4x on each plugin). It can record, too, so it's a really easy, simple solution. Of course, you'll need a real DAW to mix and master.