Crazy times hey Lionel? It must be a culture shock hearing SETI is ending after all the years you've put in to it?
Einstein@home might be an obvious choice as to where to go, it and SETI both use the same data sets. You should be able to get a similar amount of credit too. Well more or less anyway and that's with just your best 2 PC's(Einstein gives much better credit). While AMD cards seem to work best (especially on Linux) you should still do pretty well with your remaining 4 GPU's & CPU's. Then if you like it you can build purpose built rigs later on. But until you know what your doing your remaining rigs should do very well indeed on Einstein and on most other projects too for that matter. It just depends on what your after?
While it may be the end of an era for SETI crunching it could be the start of a whole new one for you.
You could even choose to do a mix of projects like most of us here do? It helps keeps things interesting, but that's up to you.
Good luck & crunch-on..