Hi Thinh, and welcome to the Decware forums ... this question was addressed recently here

The speakers he had in the above link were DALI Helicon 300 MKII rated at 86dB and most thought it would push a Torii to its limits fairly early.  It may be ok for nearfiled listening, but if you room is fairly good sized I don't think it would be an optimum pairing.  Most people who choose low wattage tube amps try to stick with speakers that are within 90+ dB range for efficiency.