Hi Maurizio,
My needs are exactly the same: recording live music and nature sounds. I bought a SP-preamp and SP-CMC4U mics. Here is my 0.2: the preamp works great both for taping music and nature sounds thanks to its two-gain-level configuration - it has a small package, works with a 9v battery and sounds good; regardings the mics, soundwise they are just great and - don't miss that - it's possible to interchange the caps with omni, subcards, hypercards and shotguns.
Another plus is the excellent Soundprofessionals' customer service - Chris Carfagno is really a nice guy and his team is committed to to the customer.
I know the budget is higher than CA's solution, but IMHO these things are worth every cent.
Just my opinion....