Wemfan,
I agree with Finsup: you may find you don't need a sub once you have it up n running and listen for a few days. You may want one since the LS50s only reproduce bass down to 47hz. I'd wait to make sure, though, since it may save you a punch in the face from your neighbor.
The possible need for a sub was the only downside I could think of when using the LS50s. If you do decide you need one, just make sure you get one with a built-in amplifier, which most come with, anyway. Once you decide on a center speaker, the A31's 3-channels will all be spoken for.
I know you received my post info on the stands after you had already bought the Sound Anchors. My recent replies have been slow to post for some reason.
In any case, you made a good choice with the Sound Anchor stands; I think they'll perform well. It's just that the Argosy stands may be just as good for a much better price.
I'm looking forward to the results since they should be very good.
I read you may be constructing some more systems in the future. If this one meets your expectations, I will be available if you'd like, at my usual fee.
Enjoy,
Tim