Yes, if you are buying a set of more than one tube for a pre-amp it would be a good idea to ask the dealer for a matched set of tubes. Yes, you would request that specifically. There are good tube dealers in other countries and far and near. Some tubes are more delicate than others, but if packed well, in general, they should ship well by air. If you receive a tube shipment in the Winter when it is cold outside you should allow the tubes to acclimate to room temperature before using them. I've purchased several tubes from overseas sources with no incident and all tubes have tested well. I bought some tubes from someone who had purchased from a dealer in Hong Kong and those tubes were not only not matched well, but one of them tested bad (in need of replacement). The guy I purchased from ended up sending the two worst back to Hong Kong. I kept the other two from the quad. Those were GEC 12AT7's. Especially when buying tubes overseas you should definitely only buy from dealers who you know from reliable sources are reputable and will stand behind their products and service. You risk the hassle of an international insurance claim if anything is damaged, and for expensive NOS tubes it may not be worth the hassle. Shipping insurance in general is a royal PITA, and it's getting harder and harder to "prove liability" and get paid for a claim. This may be even more so with Vacuum tubes where damage is not always physically apparent. Shipping is obviously also more expensive from overseas as well. Portugal is indeed in the southeast of Europe....was that a question? It's a beautiful country! Don't know any tube dealers there though, that's not to say they do not exist. I'm sure that there are good and bad tube dealers in most of the industrial countries of Europe, just like there are here. Some of the more exotic NOS seem more readily available abroad, probably since most were manufactured there. The Japanese audiophiles love tube gear I'm told, and are a major consumer of tubes and tube hardware. They do make some pretty good tubes in Japan as well, but are also known as a major source of counterfit tubes too. Again, since you're new to tubes, I would stick closer to home for now and save yourself the potential hassle. Along with my recommendation of Jon through my many experiences buying from him, you can also find many recommendations for other good dealers, closer to you, on this forum as well as on AudioAsylum. Kevin Deal at Upscale Audio, as well as Andy over at Vintage Tube Services both have good reputations among those who have dealt with them. Kevin Deal does run a full service high-end audio store, and has been criticized on these forums (he has also received much praise here as well) for giving priority (rightly, IMO) to the products and sales that keep him in business, of which tube sales are only a tiny part. The upside of that, as I see it, is that he deals with a great variety of different components and knows about how tube selection affects specific components. Both Jon, and Andy are strictly tube dealers as far as I know. All they sell are tubes and tweaks. Jon has been able to give me excellent advice about specific components as well and was right on in his assessment. Again, I have no doubt that all three of these dealers could be a darn fine source for tubes and advice about tubes. I have no personal experiences to speak of with either Upscale or Vintage, but there have been many posts recommending both as excellent dealers. Any of the three will be able to sell you a matched set of tubes, and should be able to recommend specific tubes for you application.