Just a bit confuse, need memory for computer

Hi,

I just bought a used HP Z230 i7 4790 (this is to replace my computer that died ... had a 2008 build sticker on it ... hmmmm).

The manual says "non-ECC" "4x8GB" (for 32 gb) "ddr3-1600"

I don't see a voltage so ?????

I am looking on ebay for some used memory ... I may have to settle for 16 GB because of my tight budget but I am hoping for 32 gb.

I see a lot of memory out there.

I see some had different timing (I read this is the CAS rating) .... but will this matter to me on a...

Just a bit confuse, need memory for computer