Hi Arnt m, congrats on your pces, there is allot of info. in relation to MBL101e's already in the system so just do some searches both in the amps and speaker sections. For a starter you could just refer to my answers and questions and you will find allot and then others within the thread you could do the same to get even more..... or type in to buy MBL and scrow down to forum discussions and there you go lots and lots of info.
My personal preference is not an all MBL set-up, I still own my MBL's which I'm really enjoying along with the 1621a transport, I owned the 6010 pre and had the 9008's and 9011's in my set-up along with the matching dac but they did not stay.
It all comes down to a personal preference but I know of many who have mirrored my thoughts, allot going with a varity of amps/pre combo's.
Best of luck and enjoy your journey, mine is still on going. That 1621a I own is collecting dust since I added vinyl to my set-up, need to find a good home for it, someone who will appreciate it. Huge upgrade right there from your 1521a just so you are aware, Teajay another member had the same pce as you and just recently did this, you can refer to his thoughts, he knew there would be changes but not to the full extent that he has now exsperienced.