Note the eye relief of the 16 Nagler, Type 5 is tighter than the 35 Panoptic, 12 Delos & 8 Delos. Not for eyeglass wearers and even without glasses you are up close with this eyepiece. It is a very fine eyepiece though. Did you consider 14mm Delos or if you want Nagler then 13mm, Type 6 which has a bit more eye relief than the 16. See
http://www.televue.com/engine/TV3b_page.asp?id=214
The 17 Nagler, Type 4 or 17 Delos are also good options for longer eye relief.
With regards to buying and selling until you find something you like sounds good in theory but you will find the only way to do it properly when comparing is to gave both or more alternatives at hand when you compare. Unfortunately sometimes you have to sell first to buy the alternative only to repurchase the first option again later. This is when it gets expensive!
Another thing to remember is that you will eventually end up with extra and different telescopes with different focal lengths and optical characteristics. If buying for magnification alone for one telescope you will find a completely new series of eyepiece focal lengths works better with another telescope. Also remember if you keep the apparent field of your chosen eyepieces the same then the true field of view and magnification change with the same ratio.
Whatever you choose, enjoy!