Hi,
Its been some time since I dabbled in the second hand market but in my experience buying anything with an optical drive second hand is always a gamble.
You just never really know how its been treated. Plus the fact that theres always a chance it could fail really soon after your purchase leaving you back at square one.
I'd assume a two year life span for any optical drive with regular use. Anything beyond that is
fortunate IMO.
The PX80 should scale any input very well. With that in mind, I would say wait until you can try your SD360 through it. If you feel you need an upgrade then, you wont go far wrong with any of the brands youve mentioned.
I found the Pio DV-600 to be a good performer for DVD playback in its price bracket. If SD is your primary source and you can stretch to a bit more, you may want to consider one of the later Oppo models too