2nd Monitor not detected on ATI HD 2700

Question

Here is the short version of my story. The company bought a new Intel PowerMac Quad G5 2.5 base model, NO upgrades to replace a PowerPC G5 Dual 2.3. This was due to the fact that After Effect CS4 will only run on an Intel Mac. Not a big deal until the fact that our current Xsan is running 1.42 and that will not run on 10.5. So, I downgraded the OS to 10.4.11 on the Intel Mac, set up the network and fiber channel connections and everything looks to be running fine but only one monitor will come on. The Intel Mac came with a ATI Radeon HD 2700 with dual DVI. We have a 23" Apple Cinema & a 20" Apple LDC (with a Apple ADC > DVI converter) screens. Both are working but only one will be detected on boot up. Here is what I've done so far:
1: Switched the connections, but still only one will show up.
2: Only connected one monitor but tried port 1 and 2, both ports are in working order.
3: Moved the ATI card to the second x16 PCIe slot, same result
4: Replaced the ATI card with a Nvida GeForce 6600 PCIe (was in the PowerPC Mac), neither monitor would come on.
5: Placed both the ATI and Nvida cards in the computer (could hear them yelling at each other), only the the ATI would have a monitor come on.
6: Downloaded the 10.4.11 combo update and re-installed it, same result: one screen.
7: tried to put the kitchen sink in computer but could make it fit.
8: Triple checked my connections and power, all are fine.
So, any help would be great. I just don't know why this card will not detect the second monitor. I've looked in the System Preferences and checked the profile, the card is there and looks fine.
Thanks for your time.

Answer 1

The 2600 is not supported on Tiger. There is a hack to get some type of drivers, but still not right.
What you needed was a 2007 Mac Pro 8-core 3GHz if possible, Apple Store Special had them from time to time.
http://store.apple.com/us/browse/home/specialdeals/mac/mac_pro
This hits on one area where it is easy to hit wall and hard place, there is no real backward compatibility. New hardware equals OS it shipped with. The Nvidia 8800GT needs 10.5.5+ (10.5.2 minimum but terrible driver issues) and same for Radeon 3870 (the OEM card is your best bet but limited to 10.5.2).
Which is why people hang onto and you continue to see strong prices for Quad G5s probably.
Adobe stuck to Carbon too long. And now they have to catch up to where Snow 10.6 will land.
You still want to use the "Intel G5" it seems in your layout. Maybe Apple should have called it "G6" and painted the box black!
2008 Mac Pros only run Leopard properly, even though Leopard was so new it wasn't really ready and vendors like Adobe didn't have time yet (and some had to wait for bugs and 10.5.2 to even begin to port to Leopard, besides the ".0" version changed - a lot - from what they had last seen.
You really are between rock and hard place. People really hate and detest the old Radeon X1900 for its design, heat, noise, and how it clogs with dust regularly, but at "only" $399, and already 2-3 yrs old, worth a look.
Some graphics benchmarks
http://www.barefeats.com/harper15.html