Upgrading to King Bed

Upgrading to King Bed from a Queen.

Trying to decide between a few options

1. Buy a new cover only - $1,124 (seems slightly wasteful as my old pod4 cover is perfectly fine and works, just wont be usable as ill have no Hub for it.)(Worry old cover might grow mold from not being used even if i drain it as best as i can)

2. Trade in my existing Pod4 system (hub+Cover) and buy King Pod 5 - $2,100 (no worries about old system as it has been fully exchanged, but it costs 1k more.)

3. Buy a Pod5 system and put the Pod4 on my old bed in guest room - $2,600 (the system put on my guest bed wont be used often and this costs $1,500 more)

Anyone know of some more pros or cons to each options?