Lee, since the surround material in 2-channel(or multi-channel)classical sources is ambient in nature and wide dispersion rather than tight imaging is therefore desirable, the QS4s or QS8s are ideal for the purpose.
The Celestions can certainly be used, but a suggestion as to placement would be to have them directly to the side of the listening position but aimed toward the back wall rather than inward, so as to increase the proportion of diffused sound.
Although you may not be ready at this time for the receiver purchase, I'd suggest that since a few of the excellent Onkyo 818 factory refurbs are still available from Accessories4less
for about $600, that this be considered. For a lower budget the Denon E400 is available from them for about $250.