newbie need help on decision on buying an amp

first of all ,this is my first post and want to say hello to all the audigoner.. now here is the question..i am planning to buy a tube amplifier(KR anteras) .this amp produce around 20W which is very low for my Vandersteen 3A,to listen to my normal volume level.i have to turn it up to 4/5 of the maximum level.the question is..if i have to crank up the volume level so high..would it run short on the life of the amp? over work the amp?another word.i dont know if this the the right way to run the amp?please give me some advice because i dont know whether if i should buy this amp or not?. my pre-amp is the krell 250P..thanks in advance....