I’ve tried loads of steel frames and the Soul has worked best for me. It is a very personal thing though. Try to get some test rides – I know it’s difficult with a lot of the web based sellers but folk on here are usually great at offering their bikes for a test.
I liked the P7 too but mine was nicked. PA is great frame but noticeably heavier than the Soul. That’s not a criticism, it’s aimed at a slightly different place in the market. I’ve not had a 456 but have had a few older inbreds. Very good and great value.
If you are near Edinburgh and want to try a 19″ Soul, you can try mine.