If you are mostly interested in inbound/outbound phone calls, another option is intelli-CTI from QGate.
www.qgate.co.uk/.../intelli-cti-ms-crm.aspx
Avaya is definitely supported as well as both Dynamics CRM Online and on-premise. it's pretty easy to setup and configure. You can download an eval from their website. It takes less than about 30 minutes to get it installed and configured (assuming you have the TAPI drivers installed on your desktops). We've used this for several clients and they are quite happy with it.
Telephony integration can be a daunting task unless you are familiar with TAPI/CTAPI or related protocols. In my experience it is much better to go with a supported product than trying to create your own.