Panasonic makes the Panaflo line in both 12-volt and 24-volt versions. I'd certainly recommend getting the 12-volt
If you want more airflow than 24cfm, consider the
M1A model instead of the L1A. Personally, I've never tried the M model in any size. As mentioned, the Panaflos are better than average at squeezing air through constrictions IMO, so they might surprise you even if their cfm rating seems lower. Another fan that could be worth a look is the Enermax manually-adjustable 80mm fan, which you can crank up/down to suit your tastes.
Yet another possibility is to shoehorn a 92mm Panaflo L1A into your front drive cage. You'll have to take out the plastic fan holder and figure out how to fit it in there snugly (maybe some O-rings or something soft around the edge to hold it in place). The 92mm L1A is rated for over 40cfm at 27dB and it's very quiet in real life.
Reducing restrictions to airflow improves not only the airflow, but the noise level (less turbulence = less noise), so also consider taking the bezel off of your case and nipping out the stock grillework that the fans have to pull the air through, at least for the front fans. You should be able to do a rudimentary job of that with nothing but a good diagonal cutting plier.