Speakers after GMA Europas

Another option might be Meadowlarks.

Unsound, Except size and neither the Thiels or Vandersteens are going to play at anywhere near their potential with a 50 watt amplifier.

Meadowlarks are a great recommendation.

Rrog, Thiel recommends 50-250 Watts for the 3.5's, with the possibility that in some circumstances 25 or 300 Watts might be appropriate (8 Ohm load rating assuming ss w/ the ability to double down). Remember these Thiels don't drop below 4 Ohms. Vandersteen recommends 40-160 Watts (8 Ohm rating). Your point is well taken, the minimum recommendations will not play these speakers to their full potential, and are probably only suited for small rooms without big SPL expectations. Again the used cost of these speakers allows for the expense of more powerful amplification as might be needed.
Unlike the Thiels and Vandersteens there is no available support for the Meadowlarks, or for that matter Dunlavy's (which at this price point would only include models with less bass capability and yet more physical size).

I agree that some more info is needed about the OP's room, as well as his priorities when it comes to sound. I'm with Shakeydeal - while the Vandys are great speakers for the money, I think they're outclassed by GMAs. In my experience, the first-order crossover of a GMA is of a much higher quality than the crossover in the Vandersteen 2s - the dynamics and detail are on a different level. If that's what the OP liked about the Europas, maybe he needs to stick with his original brand. In my experience, the GMA trebles also outclass the Thiels and Meadowlarks, as good as those latter brands are.

Dunlavy Audio Laboratories SC-IV Loudspeaker Specifications

Power Handling: Peak 250W for 10ms, average (pink noise) 25W. Recommended amplifier power: minimum 100W into 8 ohms. Recommended listening distance 8'-25'.