Sansui speakers are unquestionably more efficient, but IMO, what matters alot more is how speakers actually sound, and in that regard, IMO- vintage Infinity's sound alot better. And they are not that inefficient whereby any decent Sansui receiver (G-5500, 7070 for example) would have any trouble to drive them. But anyhow, if you already had a pair of Qa's and youre looking to try out a few more things, so be it, I gave you the best suggestion I could for the price. As far as Infinity goes, they made some tremendous speakers, but those particular models would cost quite a bit more than 100 bucks. In that price range, the Infinity Qb, Qa, and Qe's are very good choices.
B/F