You cannot go back two full versions of OSX to Tiger on a new Mac.
Your mac will only be able to boot from Snow Leopard and only the version that comes on your new mac's operating discs, i.e. 10.6.3. Your iMac won't boot off 10.6.0 either.
There is no way you can boot Tiger 10.4 on a new machine and it has nothing to do with Intel vs. PPC cpus. The early intel Macs all came with Tiger.
Your machine is just too new to boot off Tiger, end of story.
There are exceptions to this rule, i.e. if you bought an intel mac that was produced through the introduction of Snow Leopard.
As an example, the mac mini's from 2009. They were introduced while Leopard 10.5 was current. Then Snow Leopard came out. The 2009 Mac Minis then shipped with Snow Leopard, but if you had system dvds from the same Mac Mini purchased a few months earlier, you could boot your newer Mac Mini that had the same CPU as an earlier one with 10.5 Leopard.
In your case, tho, Tiger is way too old to be able to be booted from your new mac.