I prefer valves to solid state for vinyl but thats just me, your speakers have a sensitivity of around 89 to 90db so a valve amp should not have to much trouble driving them. Impedence may play a part but most amps have switches to select the ohms, ie 4, 8 or 16 ohms, a 10 watt amp should be ok but it depends on your budget, i ran a leak stereo 20 with a croft micro pre with monitor audio br2's with no trouble, lovely sound but leaks are getting hard to find and are expensive, a good compromise is icon audio but you would have to include a phono stage which they also make, or try a valve phono from the likes of project, what is the rest of your system, what amp are you using now. If you go down the valve route like always have a demo, you may not like how they sound, like i said earlier i prefer the sound of valves over solid state and some vice versa but the right choice can be quite beguiling.