I have a musical fidelity A3cr pre amp in great shape you can have for $675. It is a great preamp for the money and mates with a variety of amps. Would be a huge upgrade from your NAD 7140 as a pre.
That said, I have also owned Conrad Johnson's pv-10a. Also a great buy. Not as neutral or detailed as the MF, but very lush and especially sweet on vocals and acoustic guitar. If you need a phono, the version with a phono is quite good. Lack of remote may be an issue.
Remember, what sounds good to you is the right choice. Good luck.
Paul
That said, I have also owned Conrad Johnson's pv-10a. Also a great buy. Not as neutral or detailed as the MF, but very lush and especially sweet on vocals and acoustic guitar. If you need a phono, the version with a phono is quite good. Lack of remote may be an issue.
Remember, what sounds good to you is the right choice. Good luck.
Paul