It will mostly be institutional investors buying into even smaller size IPO shares -- these are savvy investors and the mania of the dot-com bubble has certainly not been forgotten.
The thing is there isn't really a huge market for these deals at the moment -- his bank specializes in deals of this size and I asked him if he thinks more mid-range banks will popup to serve this market and he said that probably not until the deal flow comes in.
The JOBS act really helps my company -- we're too far along for VC, but not far enough along for a public IPO. The post-VC, private equity market makes the most sense, but as you noted, the amount of money you can raise that way pre-JOBS act is far too low, making companies like mine (Pixar for live-action filmmaking) either at the mercy/generosity of a Steve Jobs-like figure (literally), or simply not funded at all since we exist in the Government-created financial no-mans land. Either is far from ideal.
The JOBS act, at least for our company, changes this and makes a previously non-viable-through-inadvertent-regulation company suddenly viable. That's why I supported it, and continue to do so.