Where to get used Amps, CD players?

Mid range amps, RM1500-3000 price range used unit.

Where can I buy good quality headphone 6.3-3.5mm adaptor?
And with extension headphone cable.

Yesterday go to Harvey Norman, no sell there.

I also look for a good quality Optical audio cable.

Boston Acoustic speakers, where can audition?

Some floor standers have 2units of 4inch woofer, so small.

I think at least must be 5inch to do a decent job ma...

Where to buy good surround speaker wall bracket?