I owned GMA Europas for over a year. I ran them with a Pass Labs x250 SS amp, then a Manley Stingray Integrated and finally with a pair of AES Sixpacs. I much preferred tubes with the Europas, their bottom end is not to impress, I liked the magic of the mids and highs and what the tubes did with them. My opinion, I've talked to others who had exactly the opposite findings. It all comes down to personal choice.