transformer for digital PS


I am looking to build a power supply for a Raspberry Pi as a music renderer, and I have a few questions about the transformer...

Here are a few options:

AVEL 30VA X-former

This one is a traditional toroid transformer... Should be good, right?

Here is another option:

Simon Tuned Potted X-former

This one is in a blue case with potting all over, and comes with a board for the connections.

I'm trying to learn whether there is a benefit to going one way or the other on these. Or maybe a third choice?

I'm not trying to be cheap here. I want a good quality transformer which I will then feed into a voltage regulator like this:

5a Voltage Regulator using LM338 Regulator

I looked at other options for the voltage regulator, but most are probably a bit too low power (1-1.5a) and the RPi probably needs a little more than that, especially if it is feeding power to the USB, which I expect will be the way I will go with this.

I am unsure if I should be looking at a different regulator chip for this. I'd like the lowest ripple that I can reasonably achieve.

Any thought or suggestions on the choices I have to make?