The Large Advent is not that efficient. As to whether a single ST-70 can push 4 of them to volumes loud enough for your musical enjoyment would depend on the size of your room and how loud you listen to the music. As I recall back in the '70's people used stacked Advents, stacked KLH 6's, stacked AR2a to create a larger sound field. One of the tricks I remember was to run the top speaker on each channel upside down. This put the two tweeters closer together and (supposedly) made for a more coherent sound field.
You could try it by running each pair of Advents in parallel off the 4 ohm taps of your ST-70 as you mentioned. If the sound level wasn't loud enough you could consider using another ST-70 (you said that you had other Dynaco amps. Do you have another ST-70?) and run one ST-70 on each stereo channel and use the 8 ohm taps on each amp - running one channel to each speaker. You could then use a "Y" connector on each amp's input jacks feeding both channels of each amp the same (left or right stereo) signal. This should give you about 3 dB of headroom over the use of a single amp.