Why don't you just ask three for a price and then go with the cheapest?
You don't seem to value the service very much so is there is any point in using one at all?
"two estate agents selling the house and the selling agent only gets the fee?"
Most will only do sole agency - for very good reason. The big row at the end about who introduced the purchaser.
I sold a house recently and went with the person who clearly was going to ( and did) give the best service - they were probably mid range but, frankly, for the few bob you might save with the cheapest, is it worth it?
Only you can answer that.
mf