Re: 2 speaker and sub home audio system...
like mike said above, the 340s are great speakers, especially when matched with a good sub. that said, if you are going to be listening primarily to music, the sierras will provide better sound quality. many people are running their sierras subless with music, as they have excellent bass response that extends pretty low. you could just get the sierras now and hold off a little bit on the sub. while not official yet, i think it is safe to assume there is an ascend subwoofer in the works (judging by davef's responses to questions about it) so you could save some money by waiting on the sub now and see what ascend will have to offer in that regard.
CMT-340SE2 Mains & Center, CBM-170SE Surrounds, Rythmik F15, Emotiva XMC-1, Emotiva XPA-5