Beta-alanine dosage for optimum performance?

From researching it I have found that 3.2g pre-workout is the best dosage, however most pre-workout supplements have "proprietary blends" which don't tell you the exact amounts for each ingredient included (including beta-alanine) so you can't tell if you're getting the optimum dose. If you guessed and doubled the serving size yourself then you could over consume on caffeine or another ingredient for example.

So my questions are:

> Do you know of any pre-workouts that have a good dose of beta-alanine in (and of course DMAA free)?

> Is it worth supplementing solely with a beta-alanine supplement so you can control it yourself, and then combining it with a strong coffee and some beet root juice (just as an example)?

Cheers