I'd think you would want to match performance of some of the euro rounds; Fiocci, S&B seem to have really good reputations for .32 ACP. I've shot a good deal of the Fiocci - the S&B is priced out of my range from what I've seen. I sometimes keep a .32 ACP Pistol around, just because I have one and find it easy to stick on a shelf near where I'm working, and in a little holster - does not draw any particular attention - can't tell what it is etc. I also asked S&B what their test barrel was, and they said a 3" barrel - so, in theory that would provide an uptick in nrg from the published numbers out of a 4" barrel.
One question I have about loadings and velocity is - really what would an extra 100fps or even 200 fps do in real world performance? If you were to fire at an attacker coming at you, the round would likely just poke a .32 inch hole in one side and out the other. At a 900 fps or 1200 fps speed, sure - one has a little more nrg, but generally speaking - is there any actual advantage to poking a .32 inch hole a couple nano seconds faster? Is there a practical increase in performance? If you were trying to get a hollow point to expand maybe, but from what I've seen a good many people who like the .32 ACP just use ball ammo - and accept the round for what it is.