Before changing to Astro Byond:
2 Smart card
2 Decoder
1 Dish

After changing to Astro Byond:
2 Smart Card
1 Normal Decoder
1 Byond Decoder
1 Dish

Where are you going to get the extra card for your additional decoder? If you want to keep on using your astro max, upgrade the account that's not attached to the astro max. That way you can still get to keep your astro max. The astro max cannot record HD content anyway.