Yes, both Aardvark and Echo use Motorola DSP in their products, but utilize them in different ways. Aardvark is able to add DSP effects on some of their products (not Aark 24), Echo has not been able to come up with a way to do DSP effects yet.
DSP effects aside, both companies use the same Motorola DSP. For awhile, motherboards using the AMD chipset (namely AMD-750 series...751, 752 etc) were not compatible, or did not comply to the PCI 2.1 standard that Motorola did comply to. However, this has changed as AMD has made their current chipsets (AMD 760 series....760, 761, 762) to be fully compatible with PCI 2.1.
Athlon users need to be aware of the motherboard chipset that they have. VIA chipsets will work fine in most cases with Aardvark and Echo. But if they have an AMD 750 series...they need to upgrade the motherboard to the 760 series.
BTW, AMD has discontinued the 750 series chips....but they are still out there obviously.