Preamp recommendations for under $600.00

Get an Acurus L10 or R11. These are known as good quality pres that have good mil spec components and can be upgraded easily and with great return on investment. Mine cost me $250 used. Do a Google search and you will find reviews on them and that they are popular among budget audio lovers.

I am torn between your recommendation of the Acurus R11, and Apt Holman, Jolida JD3000 and a restored Dynaco PAS 3x.

Conrad Johnson SA250, Mangnapan MGIIb, Luxman CD

I've owned 3 of the four and seen inside the Jolida,PAS 3 and Bottlehead are easy to fix, odds are great you will end up throwing the others away because they will surely need re-capping etc and you won't like the price , assuming you even find some one to do it.

LIGHTSPEED ATTENUATER