If you sell any of them, I has moneyz! =D
If it were me (like the packrat I am) I would probably keep them all and when ever I happen to have some extra money on me and I see a new one which looks cool to me and has any sentimental value heck I would probably end up buying it.
What you could do is sell the ones that you don't have any feel towards them, like you don't care if you keep them, or not and sell those ones and get some money out of it. I remember when I sold all of my Transformers a few years back, some of them I didn't miss (Optimus, Hot shot, and there was another...), but there were some I dreadfully missed (Starscream, Megs, Arcee, Sideways) and I couldn't get them back.
In the end it is your choice of whether or not to keep all of them, but an easier way (more for me) was to sell some and keep the rest.