waas gps

Removed in working condition from Cirrus SR22 G1, originally non-waas, upgraded in 2006 by Garmin. Includes 2 data cards. $4900

hello. Buying a plane w a 430w in it. If I buy a second 430w do I have to buy two subscriptions for waas in both units? Also, has a ka135 audio panel. Is there a good slide in replacement for that unit that may sound better? Thanks