Keep in mind that firing a sub at a 45 degree angle really accomplishes nothing. Freq's below around 80hz are non-directional so pointing the driver does nothing but looks cool. Think of a rock thown into a pond, the ripples travel outward from the source in all directions.
Also, corner placement will reinforce the bass freq's, however, most often this is not the best placement to get the flattest freq response, and to handle peaks and nulls in a room. You really need to experiment once you get the sub(s).
Two subs place on opposite walls will provide a flatter response across all listening positions, then just having one sub. I would watch Ian from Axiom's video on youtube, just search for Axiom Audio. If you can place one sub along the front wall, preferably away from the corners, and the second one near the back wall, that would be great. Another option is to have them on opposite side walls. However, one up front inphase with your mains is best.
Depending on your room size, one 500 might satisfy, but you will have to experiment with sub placement.
