...yes, the tube upgrade is worth it...less high-end sizzle, more low-end definition...and if you can't find the NOS GE 6072, than the Electro-Harmonix 6072 will suffice...the original Chinese tubes are usually 12AT7 or 12 AX7...the 6072 (12AY7) is a better tube for microphone applications...Good Luck! Dennis