If it does it more after you've gotten some heat into things, or in hot ambient temps., it sounds like it could be the ignition coil going out. Replacing the fuel filter wouldn't be a bad idea just in case, but I don't think the symptoms of that would show up only after you've driven it a while.

As for plug wires, I spent ~$75 on NGK blues for my car a couple years ago, thinking the old ones must be in need of replacement, but when I finally got around to checking the resistance of the oems ('92 w/ 120k miles) I found them to be well within spec., which explains why the new wires made no difference. Unless they have any visible cracks in the insulation, I'd say leave well enough alone as they hold up surprisingly well.