Shanling T80

I bought the T80 2 months ago.  Just want to here from any experienced user any cost effective way to upgrade.  Many people said the original made in China tubes (valve) should be replaced, any recommendations?

Any brother can help on selection of tubes(valves) to modify my T80.

The tubes are 6N3P

I've replaced the Chinese made tubes to Raytheon 5670 and the original 2604 op-amp to 627.  I am amazed about the improvement by only spending <$500.  The sound is clearer and warmer.