I was surprised to find that even the cheapest ones work fine, so you may want to look for one that's free after rebate. But considering that an external, all-hardware US Robotics modem that plugs into an RS-232 serial port is sometimes just $80, it may be the least troublesome option of them all. Some of the V.90 models (i.e., 5686-03 but not 5686) are even cheaper but can be upgraded at no cost to V.92, and it seems that USR's V.90 BIOSes are more likely to give V.90 connections than their V.92 BIOSes are.