The Corsair TX 650 only has two 6pin PCI-E connectors. Seeing as 6870s take two each you would have to use peripheral Molex to PCI-E adapters to get enough PCI-E connectors. The TX650 has 8 Molex connectors in total, so aslong as you don't need more than four molex connectors for fans, etc, then there shouldn't be any problems.