Wow, you've got relatives (as in more than one) with tube amps?! Cool! I think Dynaudio's require muscle, as Peter_S said. In addition to his Rogue recommendation you may be able to find a used Mesa Baron which would fit the bill. Pretty heavy though, and takes quite a few tubes. Versatility is a strong suit though as it can cycle through three different modes of amplification ranging from pentode to triode. You should be able to find one used for about $1500 but be sure they have the original packing and will ship the tubes separately. It is a beast. But should be able to grab a hold of those Dynaudios and shake up the room if you need it to. In triode it makes for a more delicate airy presenation, while the power may be just enough to keep the little Dynaudios purring nicely.
Marco
Marco