I assume your V-4's are the single ended version. If so,
the Shindo Monbrison may be worth consideration. Of Course you would be looking used, to stay at your budgeted 5K. My guess is out of the two excellent (the warm) suggestions by Samhar, you won't get hurt w/ the CJ 16LS. I had the Mk. 1, and it is a great preamp. It would be my personal preference to stay warm with the 5A's. Are you looking for a Full-feature preamp, or a separate line/phono stage.