You can also accomplish this with a simple BOSS EQ pedal set fairly flat but with the 800s slightly boosted. Will tighten up the bottom end and make the OD more defined.
Really though, change speakers before you go modding the amp. As an owner of BOTH the JCA22H AND JCA24S the speaker difference alone will be massive. Personally, I think this amp sounds awesome stock and will most likely never mod mine. I played a rehearsal with the JCA22H through a Splawn 2x12 with Small Blocks and hung with a Mesa IIC++ into a 4x12, and I do the lead work. Remember, your speakers are pretty much the last thing your sound goes through before it hits your ears.