The Concentra II is a fine integrated amp, as are the BAT VK-300SE and the VAC Avatar Super. These are the best integrateds I've heard.
Once you get into seperates the combinations get more mind-boggling. A lot of good sound is synergy, which can take time or luck to stumble over. The best sound I ever heard out of my Beethovens came from a Classe CP-60 preamp and a Threshold T400 amp.
I was using a Classe CA-200, which sounded very good, when I was taken by the sound of my friend's Threshold T400 (he was using a CP-50 with it). When he decided to move into HT and sell the T400, I tried it in my system (Beethovens at that time), and the music it made with the CP-60 was the definition of synergy. It was magic. Better than the sound of the Threshold T2 with the T400 and better than the sound of the CP-60 with a CA-200.
Naturally, I couldn't stand still, and have since sold the Beethovens and the CP-60. I now own the VA Strauss and a BAT VK-31SE preamp. Most times I think they sound better, more definition for sure. However, I fondly remember the music I heard with the CP-60, T-400 and the Beethovens. Time can play tricks on the mind, just like remenicing about past girlfriends.
Bottom line is you'd probably have a better chance of getting very good sound right off the bat by starting out with one of the integrated amps first. That is unless you get a chance to audition a combination in person that strikes your fancy. Trying to mix and match, sound unheard, is not recommended.
PS. Congrats on the Beethovens, they are great speakers.