Spacey, I totally agree with the other posters...
...and given my own experience in being at the receiving end of women's intuition (not always a pleasant event!), your wife has probably known (or at least suspected) that something like this was in the offing for some time now. The presumed "find" in the basement would just add more creedence to those prior suspicions.
The fact that she did not freak out on the spot and knows that you are already seeing a therapist to deal with issues that you have difficulty in talking about openly work strongly in your favour that your wife would be quite receptive to your opening up to her about your crossdressing. That said, you must make sure that you control of the time, circumstances, and contents of the discussion when it does take place so that it is conducted in an appropriate and constructive manner. You also need to be fully prepared to truthfully answer the usual " Are you gay? Do you want to have a sex change operation?' etc. questions that will invariably arise during such revelations.
If you research past posts on this forum, you will find a wealth of information and advice from fellow crossdressers who have already "been there, done that", as well as advice on what landmines to avoid. You might also want to take a look at the website entitled "A Crossdresser's Secret Garden" which can be found via this link:
http://cdsecretgarden.femmegetaway.com/index.html
I, personally, have found this site to be a great resource regarding advice on how to proceed with disclosure of our crossdressing to our loved ones, as has been this forum in helping me fully accept this part of me. As others here have also alluded to, taking the plunge and coming clean to your SO and immediate family can be extremely daunting, as one can never predict the ultimate outcome with 100% certainty. But like the first parachute jump, it becomes easier and easier to do with each successful repeat, and the sense of relief and unburdening is indescribably liberating.
My wife has known about "Leslie" for many years now but we still face rocky times on occasion, and I attribute much of that to the historical legacy of the very unfortunate circumstances under which she found out about my crossdressing. By contrast, I finally (and with much apprehension!) revealed this side of myself to my adult children on separate occasions over the last 3 years, but in the manner that I have recommended to you. It went far better than I could ever have imagined, both proved themselves to be fully supportive, and there has been absolutely no negative fallout to our existing excellent relationship. My only regret now is that I didn't do it sooner, and I think that everyone in our family is relieved that this "elephant in the room" has finally been dealt with conclusively.
One can only hold such a deep, dark secret bottled up inside for so long before it either leaks out, or else the strain of trying to manage and contain it becomes unbearable.