I'm not sure I get the point of the whole exercise. It seems like the cost of SSD is more than the Mini 9 is worth these days. No matter what you do to it, you're bottlenecked by the speed of the N270 chip. I just picked up a Dell Latitude 2120 for $50, shipping included, and it has 2GB RAM, a 320GB HD, and an Atom N550 chip. The N550 clocks in at 1.5GHz, but it's dual-core, so it actually benchmarks about 90% faster than the N270. Even so, I can only make it usable by installing a lightweight Linux distro like WattOS on the thing.
My own Dell Mini 9 has only 1GB RAM and a 32GB SSD, but I can't see investing any more into it at this point.