Integrated Amplifier for Fritzspeakers Carbon 7

So far I was listening Carbon 7 with NAD C275 and Rogue Audio
Perseus Preamp tube preamp. Bass is deep and tight but highs
are kind of rolled off, It could be because of Scanspeak
tweeters. So I'm looking for Integrated Amplifier linear or
forward by nature. I would really appreciate opinions.
In looking at your system pics and comments, you say:

My Simple System
Very simple system but great sound. For source I'm using
computer with upgraded DAC
Kiza (System | Threads | Answers | This Thread)


05-19-10: Kiza
I'm more than happy with the sound. My friend also ordered
Carbon 7. Later on I will upgrade the Preamp and that is it.
Thanks for Your suggestion about Carbon 7.
Kiza (System | Threads | Answers | This Thread)

So, what changed since then ?

Get a Jadis DA-60. It is a great integrated with no sacrifice in the treble extension or detail. Just roll the 12AX7s to 5751s and use really good 12AU7s like Amperex 7316s. If you really want to extend the treble try to get the "silver bullet" now NOS Ei 12AX7s or even the scarce Sino/ Shuguang 12AX7 C9 not the common not good IMHO 12AX7 B8 . Other choices for a good top end tubes include the perennial favorite Telefunken but other German non RFT tubes have that character.
You can choose from most of the popular octal based power tube family, meaning anything from an EL 34/ 6CA7 to a KT77. My favorite is the Gold Lion reissue KT-88. My old pal Trelja much perfers the JJ E34L Blue glass in his Jadis. Experimenting is a bit expensive because you need fairly well matched octets due to the auto bias feature. I hear only good things about the GL reissue KT-77s as well.
I am saying all this in half jest, I do use a Jadis DA 60 with great tubes, my recommendation is quite real. But...You didn't mention how much you wanted to invest in your new amp. If you can find a DA-88s which has finally (I think) replaced the DA-60 in North America I would opt for that but we are talking lotto money in my world.
Ask Fritz; I recently picked up a pair of Carbon 7s from him as well and we were comparing notes on what worked and didn't. I did not like the sound of the speakers with the HK 990 - so much so that I sent the amp back.
While I like the amp, my feeling is the NAD is the weak link here. Try replacing with an Odyssey Khartago amp.