McIntosh MC240 Amplifier sound?

I recently took delivery of a restored MC240 amplifier. It came with non-descript Chinese tubes. I replaced the 6L6 with vintage RCAs and am awaiting a compliment of Mullard Telefunken mix of input tubes. At this point I find the sound to be very soft and lacking any definition. Is this typical of what I can expect with this amp or will better tubes transform the sound significantly? I'm rather surprised since from what I've read, this amp is considered to be 1 of the better amplifiers McIntosh produced all those years ago. Frankly its the softest sounding amp I've ever owned and there have been several over the years. Any observations are welcome especially those who have owned or own an MC240.