I would definitely recommend replacing the 620. Use the New 7005 controller. It is about the cost of an AP and has some other tricks up its sleeve like stateful firewalling, application visibility and control, web URL filtering, and it can be powered from a PoE port!
For more info, see here - http://www.arubanetworks.com/products/mobility-controllers/7000-series/
You now have 3 choices for 11ac APs. If the customer is budget constrained, for the same costs roughly or maybe a bit less, they can get the 7005 + the AP205s or the AP215s vs the 225s.
For this install, since the AP205 is the 11ac replacement for the AP105, please consider this as it's the same cost. For better performance, consider the AP215.
Thanks
#AP205