HELP! any suggested preamp for Harman Kardon HK775 monoblocks?

Hello everyone.

I have got a pair of Harman/Kardon HK775 monoblocks which I really like.
Until now I've been using them with the HK725 pre of the same series and Quadral Shogun MK IV

I feel that the HK725 is the weak link in my set and therefor I'm thinking of replacing it with an other Preamp.

I am searching for a 200-300 EUR second hand preamp, and would like to hear your recommendations for a preamp that will fit my set.

I play LP's and CD's 99% of the time. love warm and detailed sound.
I listen mostly to Rock, Folk, Acoustic music.
No Jazz and Classical...

I've been offered to get a Luxman C-02 for 200 EUR , any pros / cons about this preamp from your experience?

Looking forward to hear your input.
Cheers,
J