Steeeeeeeeeev - O, Steeeeeeev - O .
I've never had a Huntsman but, I've had a few Daystates and, they've all been spot on - I only got rid because the electronics and the service costs make me cringe
I've had a 510 Ultimate Sporter that was also very good. I like Air Arms so, from your choices, my recommendation would be the 510
But, don't rule out the HW100 - Best all round sub 12 pcp that money can buy
Better still, with your budget, buy a proper rifle like a TX200 and, still have enough left over for some pellets and a back street knee trembler w