Having just read a review of your amplifier, it seems to me your system is pretty well matched. No doubt a tube integrated amp would give you a more natural picture into the music. Tube amps from companies like Conrad Johnson are generally reliable and tubes should last in the 1000s of hours.
Rather than upgrade what is already a well matched system, why not get a good quality streamer and DAC. The streamer will open up a world of music discovery all controlled from an ipad/iphone, and you never need to get up from your chair like you do to change CDs. Additionally, the high quality DAC will improve the sound of your existing CDs. Use the digital output of your CD player ( which has an average at best quality built in DAC) into one of the inputs of the new DAC. I'm particularly fond of the R2R Non oversampling type DACs....smooth and more analog like ie the Denafrips or Musician Lines.