Wanted to control brightness up and down, pulsation to music/sound etc..
I'd start with the lighting effect, and make sure you're happy with that before building it into your speakers. IMO something that blinks with the music, or almost any single effect can get boring after a couple of minutes.
I'd probably go with colors or make the LEDs make the LEDs individually addressable, or at least addressable in groups. I've made a 4-channel AC lighting effect that can run 4 pairs of colored floodlights, or 16 smaller white floods in a different arrangements, or it can run a 4-channel rope light with many lamps. It's got 7 different modes, including chasing modes, a flicker mode, a toggle mode, a VU meter mode, a Knight Rider (Larson Scanner) mode, and a couple more. All of these modes come-up randomly and run for a random amount of time, they are randomly be reversed, or inverted.
The flicker effect is the simplest. In it's simplest variation the LAMP/LED comes-on when the volume is louder than average and turns off when the level is below average (I keep a 20-second moving average of the "loudness"). Inverting it means the lamp is off when it's quiet and on when it's loud. But, since I have more than one channel, I can set up a random (or not so random) pattern with some LEDs on and some off and change to their their state with loudness.
I've built a similar 7-channel effect for the Eight strings of 7-lamp rope lights in the ceiling of my van (these are small incandescent lamps).
And, I've built a "Giant VU Meter" stereo VU meter effect with 24 individually addressable LEDs for each channel. The VU Meter" also does the other chasing/blinking patterns and in all of the modes (including the VU meter mode) can be reversed (so the meter goes down with loudness, instead of up) and it can be inverted (so louder music turns more LEDs off instead of on).
The random variety of modes and variation of modes makes it a little more interesting... I never know what's coming next!