Identifying the "right tubes" is not an exact science. You can definitely exact match tubes for their electrical properties...but that's just cork sniffing in my opinion and not relevant in a well designed audio amp such as the leben. To me the right tubes are the ones that are not way off from each other...and are reasonably in the ball park. I do not chase perfectly matched quads etc
So with the above in mind; most of the power tubes I buy from ebay are strong testing singles or pairs (not necessarily matched). Once I have enough if these I just roughly match them for use in the amp. Also buying singles are a lot cheaper than the ones listed as matched pairs/quads etc.
Most of the El-84's I buy are the sittard produced ones with the d-getter. They come in different labels...but the most common ones are Amperex or Philips Miniwatt. You can determine the plant they were produced from the date code. some sellers will mention the date code and some wont. You just have to ask the questions before you commit to buy.
A good example of El84 listing is currently on ebay here:
http://www.ebay.com.au/itm/1-pc-NOS-Philips-Miniwatt-EL84-code-rX2-X5k-tested-108-6BQ5-D-getter-rare-tube-/361213641587?pt=LH_DefaultDomain_0&hash=item541a02c373