You will get the same excellent voice quality once your adapter is successfully configured with axvoice. However, guarantee terms apply only when you use Axvoice's plug and play adapter.
And
Yes definitely linksys PAP2 adapter is compatible with Axvoice service. Configuration details are given on our website
http://www.axvoice.com/support/linksys-pap2.html but you will be able to configure your adapter only after sign up and account verification.