New tubes take between 75-100hrs. to fully break-in. and even after that the sovteks are still not going to sound that good. If money is not an issue, nos tubes will sound the best. Particularly amperex 6dj8's made in holland in the early to mid 1960's and of course the siemens-halski are suppose to be the best of the best. Unfortunately, the prices are very high(anywhere from $200-$300 pr.)sometimes you can find for $150 pr.
As was mentioned before the electro harmonix's are not bad for current production tubes also, the 6h23 russian tubes are not bad for the money either($27.95 a piece) but for my money the matsushita 6dj8's are the best of the lot after the amperex, siemen's mullard's and they can be had for $30 a piece from the the Tubemonger.