You should consider fueling and engine control upgrades earlier than that, actually.
You have two choices: Top-feed or Side-feed. You can usually get used side-feeds for fairly inexpensive, although top-feeds are definitely cheaper when talking new injectors.
www.wolfkatz.com supplies well-made rails for both of these types of injectors, at a very similar price. I highly recommend them.
The background comes from the stock rail's very small bore. It causes a pressure drop across the rail when using a larger pump. That pressure drop can change the fueling as much as 10%! Hence, the need for a larger rail when you get a larger pump.
If you are using larger injectors, then the stock pump is almost maxxed out, so it's recommended to buy a larger pump when going to larger injectors.
So, more power means bigger injectors, which means a bigger pump, which means a better fuel rail.