Like the other poster said, there really isn't much of a difference between what most consider "prop" vs. retail anymore (a lot of "prop" firms are just large retail accounts). The leverage is one, being in an office surrounded by other traders is another. Most prop firms have on-sight tech support, and many have access to programmers if that's something you're looking for. A lot of prop firms offer training, but it often isn't very good and it doesn't sound like you're looking for that with your experience. Prop does require a series 7 (and other licenses) in most cases.
If you don't need most of these things, retail is probably the way to go. If you do, maybe prop is the way to go.
Of course, with technology, you could always "talk" with other traders without being in the same room. Rates really aren't much different anymore, data fees are somewhat higher for licensed "professional" traders, but that shouldn't be too much of a factor if you're successful.
Hope this helps.