I assume you are taking about just extending the frequency response of the speakers that you will use in the dining room, and not about a dedicated LFE channel? (you mentioned 2.1 in your subject title).

If so then one on the subs mentioned above should be fine, so long as they have high level (speaker level) inputs/outputs. Use the speaker level to connect the sub to whatever speaker distributor you are using, then go from the sub to the speakers. Getting a sub with variable cross-over adjustment would also allow you to better mate its performance with the room speakers you choose.

If you did mean dedicated 2.1 (left, right, +LFE) then please elaborate on it. I haven't yet heard of it here (but then it can take a while for some technologies to filter their way down under)