Question about set amps and low sensitivity spkrs

Hi, In about 3 weeks I will take ownership of an 18wpc SET integrated. I currently run an Arcam SS amp with B&W 602 S2 speakers and I'm still undecided about new speakers (more sensitive, tube friendly) to mate with my new amp. My question is, can I run my current 90db sensitive B&W speakers with the SET integrated without doing damage, or shortening the life of my new tubes? I'd hate to have the amp sitting in a box waiting for me to decide on new speakers :) I frequently see that B&W speakers don't mate well with tubes...why is this?
thanks
Michael