Very good point. I've never quite seen why the equinox would be of importance to ancient people. Solstices yes, but why the equinox? On the other hand, Orion is a great striding giant in any culture and is even impressive in my light polluted city sky.

"With so many sites pointing east how many are there for this and how many are really for the equinox sunrises?"

I gotta say that I'm agin the equinox but also agin Orion.
By my reckoning (or at least starry night pro's software) the sun on the Autumnal equinox 4000 thousand years ago rose closer to south east than east but really thats just a minor point.
My theory is that monuments were aligned east-west because east & west were THE major cardinal points of prehistory. I reckon north & south were prety much irrelevant.
What happens in the north and south ? not a lot.
All the major solar and lunar events happens within the two sectors, south east-north east and south west-north west.
The weather comes from the west,
Most of our rivers tend to run east-west or west east.
Our prehistoric geographical location is the islands stuck on the western edge of the european landmass.

So for what it's worth, I gotta say that I don't think Orion has an awful lot to do with monument orientation.
I think it's more to do with primarily the sun, the moon. And Secondly , the weather and our geographical location.

The Thornborough Henges have three alleged Orion links, so far as I'm aware.
1. The henges are arranged in a bent line, very like (perhaps 5% error) the belt stars (and like the Giza pyramids)
2. The Time Flyers programme (Nov 2003) had Jan Harding (the Newcastle Uni archeologist) and Clive Ruggles (the Leicester Uni astro-archaeologist) agreeing over how remarkable it was that Orion was framed by the south-south-west gap in the Central Henge in mid August. (Were they talking about late at night? Or about how things were 4 or 5,000 years ago?) I didn't get what they were saying (extra info seemed needed) but was impressed by how much they were impressed.
3. George Chaplin (Thornborough campaigner) recently reported Newcastle Uni (perhaps Jan Harding again) had noted that Thornborough Cursus (directly under the Central Henge) seemed to be pointing at where Orion used to set 5,000 years ago.
(All a bit third hand, but it may be worth pursuing.)

Gerry