here are some answers from my experience
1 - absolutely positively YES bookshelves are completely capable of performing just as good or better than floorstanders. i think lee bailey posted some speaker setup links that help you integrate speakers into your room. there is also a very good discussion about a BFD that helps you fine tune your sub. one user on avsforum just sold his paradigm studio 100 v.3s for the studio 20 v.3 model. i preferred ascend's cbm-170 over another company's $1499 floorstanding speaker. i know another gentleman who sold his paradigm signature S8's for the S4's. all three of us used bookshelves because we preferred them over the floorstanders.
2 - you receive a cost savings with ascend's net direct business model
3 - your receiver is a good match for the efficient speakers
4 - stable. i have mine filled with sand. we had a small graduation celebration at my place and no one knocked my 340s over.
5 - the m60 is an excellent pair of speakers, though i preferred the 340 as a center over their vp150 and consequently wanted a matching L/C/R setup.
i don't know of a cd that would bring out any trouble areas in axiom or ascend speakers. just differences really. use a wide range of music. i prefer to listen to various materials that might include distortion guitar (van halen, metallica), piano (beethoven, chopin), heavy vocals (u2), live acoustic settings (neil young, dave matthews), etc. no particular order, but those give you a pretty wide range of music as well as an idea of the reproduction of that music. don't avoid using what you like best. couple what you like best and what sounds best to you, then you'll pick the best speaker for you. i always used my favorite cds, and i felt confident that i made the best decision for myself.