Vintage Onkyo gear vs Adcom

Looking for some help on the budget upgrade path:

I currently have an Adcom GFP-565 and have been searching for a power amp to do it justice.

In the course of my research I have stumbled upon quite a few Onkyo integrateds from the late 80's--early 90's (a-8800, a-890 to name a couple) that look very appealing.  I have heard the Adcom and also some Onkyo stuff from that era and they seem much closer in performance than I would have guessed.

So my question is this: should I continue to pursue a power amp for the 565 or sell it to purchase one of the high end Onkyo/Integra integrated?

Thanks