I'd like buy Power Mac G5, Logic 6, Motu 192HD and MTP AV, but I don't know if is compatibily. Anybody knows?

http://www.motu.com/english/other/g5/body.html

The G5 introduces significant enhancements to the PCI architecture, along with a required 3.3-volt card format. As a result, existing PCI-424 cards do not fit in the G5's new PCI slots. MOTU has developed a modified 3-volt PCI-424 card that is fully compatible with the new G5 computers. In addition, an affordable trade-in program is now available - see below for complete details. This new card is the PCI-424/G5 card, and it works in the new G5's, as well as any earlier PCI-424 compatible Power Mac (G4, G3, etc.)

PCI-424/G5 trade-in program
Existing PCI-424 owners can trade in their PCI-424 card for a new PCI-424/G5 card for $69, plus shipping. This program is available to registered owners of a PCI-424 core system:

2408mk3 core system
24I/O core system
HD192 core system

PCI-324 owners are not eligible for this trade-in.

PCI-424/G5 cards should be available by late August or early September. Trade-in orders are now being taken. To place your PCI-424/G5 trade-in order, contact MOTU customer service in one of the following ways:

by phone at (617) 576-2760
by fax at (617) 576-3609
by email at upgrades@motu.com