I'm not sure about getting DSP manager to work with stock. I'd ASSume that it's just a matter of finding a version that'll work with the revision of android you're running on, but it could be more complicated than that.
Beats is really going to require a pair of headphones that have a good decoder or sound processor built in. Noise cancelling headphones (some of them) have these, but most don't as they're just vented to let a little sound out in order to drown away sound near the headphones. For beats to shine using just "any ol' headphone" won't really work. You may notice a small, medium, or even a huge difference but it would depend on your headset. I've got pictures up in the thread showing frequency spectrum readouts that clearly point out that the beats dsp does work, but to what avail is questionable to each person. The thing to point out here is that NONE of us, not even my audiophilistic ass, can hear like a computer can. Even in my car I've got six 5 1/4" cerwin vega speakers that range from 8-26,000 Khz and I STILL can't tell a huge difference between those and the stock speakers that only go up to 20,000hz. Probably because my ears have blown out from years of "pumpin' bass." Everyone will hear, and process things a little different depending on how bad their ear drums are, and how clogged their ears are, and how their brain interprets sound. I know that sounds stupid but that's my way of saying "a weetawd wown't heyr da sayme way we wheel." (No offense to anyone that's Intellectually Disabled. I'm just pointing out that due to certain situations people hear things differently.)
Anyways, I'll check out getting dsp to work on a few different roms today, and will let you know what I find out if anything.