I have been really enjoying the SSL Mixpander5 PCI card (PC only) with Alpha Link AX converters. It has plenty of DSP also, and you can purchase as a download / unlock code the exact same SSL EQ that the Duende units ship with. The Mixpander5 card has enough DSP to run all ins and outs of the Alpha Link converters simultaneously up to 96k & also handle 20 instances of the SSL EQ for example.
In the low $4,000 range you're talking 24 I/O and plenty of DSP power.
Oh, and they sound absolutely fantastic.
Been using with Nuendo 4 for months now, it has been 100% flawless for me.