I don't know if there's something either higher up that you'd qualify as "can readily buy", but a [Raptor blackbird](https://www.raptorcs.com/content/BK1B01/intro.html) would handily outclass the legacy PPC macs, and a [Talos 4U server](https://secure.raptorcs.com/content/TL2SV2/purchase.html) (with two CPUs up to 22 cores each) would pretty much crush it.

Admittedly the latter is a $15k machine, which is perhaps may be pushing what you had in mind for "can readily buy", but it's for sale...