for me, i prefer to buy the following audio gears:
receiver-as brand new
front,center, surrounds speakers-as second/third hand
subwoofer-as second hand
my reason is that generally, receivers have shorter lifespan than speakers and sub, being a mere electronic item (baka may issues na mabili mo hence no peace of mind kasi mahal magpaayos ng receiver.)
im not comfortable though with entry level receivers like pioneer 531 because of weak power. pioneer 930 is way better if you can allocate a bit more of your budget, or onkyo 737.
kung walang issues/sira, i chose onkyo 545 over 636 mainly because its a bit newer generation than 636 (656 na ngayon and 555).