I don't have the keyboard, but I have two racks of AS modules, as well as some Doepfer, Bananalogue, Cynthia and home made modules.
The AS gear is well made, and good sounding, it also seems that eurorack is the fastest growing format, with the most choice of modules available.So AS is a very good starting choice, reliable and well thought out, an excellent choice for the basic system you are considering.
Only negative I found with AS is an eccentric attitude towards sales. Both AS in England and their US distributor, make it difficult for International customers to purchase..no credit card facilities and Big City music did not reply to my emails requesting info as to how I could purchase an AS sequencer.
Following an unpleasant email correspondence with the prickly Bob Williams of AS when I complained about this, I decided to cease dealing with AS, and started buying Doepfer instead. Doepfer are less expensive, and offer better service through Analogue Haven and direct.
Doepfer gear seems fine to me, if not quite as solid as AS. My experience with AS is that they need serious advice on customer relations and sales.
Red inside, same as Queen Victoria. Getting redder by the minute.