I was also a pistol lover for the longest time - until I started using the Plasma Rifle and finding it even better.
As for the amount of ammo to carry? For me, 600 was actually my minimum, and I'd try to carry around 900 or more rounds. If you're at a deeper level and there's no captains around, you can go through ammo pretty quickly fighting through crowds of high hp enemies. (And now that I play with chainguns it's 800 minimum and 1100 optimal, yikes.)
Magazine mods are pretty great for pistols though, especially for your off-hand (prepared) slot. I'm not sure if other players do this often, but I actually use regular reload very often (with dualgunner), and then only dual reload once the regular reload is over and no enemies have come into view, as dual reloading right off the bat could take over 2 seconds, plenty of time for enemies to come into view AND get a shot off. I like to have a damage modified pistol for my main weapon, though, to give that extra edge against armored foes. With this combination I might fire, say, four dualshots off to kill an enemy I see, single reload, then notice an enemy has come into view while I was single reloading, then still have four dualshots remaining as my primary pistol has 6/6 ammo while my secondary has 4/8 ammo. If I had dual reloaded in this situation, that enemy that just approached would have likely gotten a shot off.