Well, as a general rule any external modem is a hardware modem, so if you pick up a USB v.92 modem you'll be OK.
As for PCI, you'll actually do OK with whatever you get. The old ISA Winmodems were really crappy, but the PCI Winmodems are much better because not only are CPUs much faster, but the onboard DSP is much better and the PCI controller also offloads a lot of the crap. I have a PCI Winmodem in my 800 Mhz laptop and I only get a stutter in my mouse and the rest of my system in the dial and hang up split seconds, but the rest of the time it's fine. The PCI modem in my 1.6 GHz P4 is the same way.
If you MUST HAVE a hardware PCI modem, I can't help you there.