I don't know that there's a single best place.

It's probably more important to pick your pump -- based on load and pool piping -- BEFORE you start shopping. Then, you can find the best price on that particular pump.

You should keep in mind that replacing a pump can be a little more difficult that what you describe. Unless you get the SAME model, it's not likely the existing piping will be lined up quite right, and you can end up replacing quite a bit, just to get the alignment you need. Also, you need to replace the electrical connection. Keep in mind that not all "2HP" pumps draw the same current.

But . . . do you really need a 2 HP pump?