Thanks for the replies chaps. Ian, I've answered your other post.
I should have said, I want to use a 1U PSU ideally (or a brick/picoPSU, but this looks like a more expensive option to me). I have a 120W already, but it's 20 pin.
I can either buy a 20 to 24 pin converter, and see if the 120W works, but I'm wary of this option as, at the end of the day, the PSU was not designed for this.
Or, I can buy a different, low-powered PSU with 24 pins and hope it works (this is why I wanted to know how many pins the bundled 90W one from newegg has, if anybody has this?).
Or, I can buy a proper beefy 400 - 500W PSU (20 or 24 pin) and be fairly certain that it will work (I'm currently using a 450W ATX PSU with 20 pins).