Retubing dilemma


I have a melody el34 integrated amp.  As I mentioned in a older thread one of the tube store el34 preferred series tubes went up in flames. So now I have a choice and I want to see what people think would make the most difference sonically. I would like to keep this under  $200. 1.  I currently have 2 northern electric 6Sn7 tubes and 2 shuguang treasures 6sn7 tubes, 1 of each type on each side.  Should I replace the northern electrics with shuguangs so I have a full set all the same and just replace the el34 with the same preferred series or
2. Replace the el34s with gold lion kt77 that seem to be very well liked. 3. Other suggestions. 
As an aside if I went with #1 should I move the old shuguangs to one side and put the new pair on one side. 
Thanks 
jkontuly
jkontuly, you need to start reading my posts. I’ve got a Melody and have warned many times about my Preferred Series tubes going up in flames. Three in two months, failed spectacularly. Worst of all the tubes tried in my 30 years running tube amps.

The tubes you seek are JJ. Very reliable, very affordable, yet very close to the best sounding tubes JJ are the best deal in tubes I have found.

You can buy them from TubeStore.com, they are a good source, just not for their Preferred Series tubes! As for the other tubes leave them alone. Unless of course you like playing the lottery.
There’s a lot of good information here, regarding 6SN7 tubes: http://www.dehavillandhifi.com/6sn7_vt.htm       Far as whether you should have two of the exact same iteration/manufacturer, in each amp: pay particular attention, to the third from the last paragraph.