You can pick up the AR20 for a lot less than £500 second hand, I payed £350 for a 3yrs old one, and a club member has just exchanged one that was leas than a year old for £400.
They are a very accurate rifle and fully ajustable but heavy, love my one but then I have done a lot to it.
Also had a s400 and wished now that I didn't sell, again its a supremely accurate, lightweight, simply to work on great rifle.
Try them both out, see what one fits the best then look around for a good quality second hand one at a good price.
Steyr Hunter HFT/ HW 100 barrel + s111 & SS buttplate. HW100Kt+ SWFA ss 10x42......Shooting HFT for MVAC.