The version of the IPOSOE that I have has four analog station ports, there's another version with no digital stations and eight analog ports, so there's some possibility, but you do have to hunt around.

Something like an IPOSOE or a Nortel BCM50 will probably cost you a little less than an FXS card a dedicated PC good enough for Asterisk, at least from what I've seen. The other challenge is that if you want to dial from one machine to the next, you'll need FXS cards with two ports, or two or more FXS cards, just dependingo n what you want.

The one thing I'd like to see is if you can configure an Asterisk box to directly accept dial-in connections from computers, so that instead of dialing into one another, they dial into the asterisk box as though it were your own little ISP.