Ben's (SolaScriptura) advice is very good. And, unless there is a specific reason for which you are quite directly set on these particular volumes, at this stage of your learning it might be better to focus on individual volumes by individual authors, instead of large sets which may contain many volumes you won't find as useful as you begin to discover other things.
Regarding volumes of the apostolic and post-apostolic fathers: If your specific purpose in studying and life is to become a student of Patristic studies, then such a purchase could be a good investment; however, if you're simply looking for the Christian literature which will be the most useful in your Christian walk, purchasing 38 volumes of the fathers may not be the best investment. You could, perhaps, selectively read certain patristic authors and works in which you have an interest online, and if you find yourself strongly drawn to or interested in one, then you might seek to purchase works of that author.
Re: Luther, I think much the above applies here, as well. As Ruben says, Luther is most certainly not read enough, and you will find much edification in his works. But, given the nature, structure and form of his works, one has to ask if $650 and 30+ volumes all at once and without specific goals or purposes is the best plan. Maybe it is. I don't know your goals - it might be to be a Luther scholar.
Owen strikes me as the most sensible of the options for a Reformed believer if you are looking to buy a complete set (though you should take note, the 16 volumes is not his complete works - there is also the volume of his Latin works [and that was translated into English a few years ago] which was left out of that set, and also his 7 volume commentary on Hebrews, which is sold as a different set). You'll find little regret in reading almost any of his works, and he presents solid Reformed teaching on a great many topics (though he does, of course, present a few aberrant views).
If you are truly looking for "sets" or complete works by different authors, there are a few other "complete works" sets of Reformed (puritan) authors which are in almost every way equal (or superior!) to Owen. Sets have been published of Thomas Goodwin (the absolute best of "complete works" sets published, in my opinion!), Thomas Manton (as mentioned above), Thomas Brooks, William Bridge, Richard Sibbes, Thomas Boston and (I believe) a set of William Perkins' works is in the works, though I'm not sure on projected date of publication; in addition, though it's not a complete set, Naphtali press has published a good amount of James Durham's works, which is just as worthy as any of the above mentioned sets.
If you're willing to not require "complete sets," I think you may find purchasing individual volumes may serve your interests even better - though I am a big advocate of picking one author who has written a massively wide variety of types of books (exegetical, homiletical, polemical, topical, systematic, catechetical, etc) on a great many subjects and dealing thoroughly with that author for the duration of your life.
Lastly, I'm sure you are aware, but just in case - there are far more works of Jean Calvin out there than you have, simply for the fact that most haven't yet been translated (and many of them not even published in the Latin or French). So even once you have his Institutes, his sermons, his commentaries, his OT lectures, his tracts and treatises, his discourses, his letters, etc., which have been translated, there is still a massive amount of literature waiting to be translated. Look forward to it!
