I have been an almost completely dedicated CD3000 user and have heard them with virtually everything available (excepting Nik's amp, and the latest, top of the line post -Supra ear amps from Singlepower).
They definitely sound best with tubes, IMO, as it tames the slightly overextended treble just perfectly. The best amp I have ever heard them with is Jude's Antique Sound Labs Twinhead Mk II (the famous CES Ringer amp). However, production MkII's have never lived up to that performance and thus, it isnt available. The second best amp I've ever heard them with is the Cary SLI-80 Signature Integrated amp, which I bought to pair with them.
Other amps that work extremely well with them are the second generation Singlepower Supra, and, at a substantially lower price, the PPX3.
I have not personally heard the combination, but have been told, by people whose ears I respect, that the Moth Si2a3 sounds incredible with them, and may equal or surpass the ASL Twinhead Mk II ringer amp. I have the new, upgraded and ultimate version of that amp on order now, and will report back when I receive it.
If you, for some reason, insist on going solid state with the CD3000's, of all the ones I've heard, the Emmeline HR2 cannot be beat in that class, and its steal for the money. I simply find good solid state amps in combination with the 3000's too strident and difficult to listen to for any extended period.
I hope this helps.
JC