THe X100P is essentially a modem card. It can be problematic to get working well with asterisk in terms of fully supporting line signalling and call quality. The general advice is to use one of the more modern options. I say this in an asterisk context, as I have not used linuxmce yet.
Under asterisk we use an E1/T1 digium card for our ISDN32 line, and spa3102's for analogue lines (we also have a GSM gateway for connecting to mobile phones). I can recommend these solutions over X100P's (I had a few, and abandoned them). I know that people also have good experiences with the modern FXS/FXO digium cards.
You may get an X100P (original or copy) working, they are supported on a legacy basis, but they are not recommended. At circa £50 (UK pounds) I would recommend the SPA-3102. It's reasonally low cost per incoming analogue line. It gives you 1 FXS, 1 FXO (allowing you take an incoming line and convert it to a Voip channel for your switch - asterisk in this case, and also provide a Voip to analogue phone output channel - I use it to connect to a DECT base station so that nontechnical users can use an "ordinary phone"). Worth the investment, in my view.
