I have the same exact settings but I am not using the onboard video (HDMI). However, if you get it to work I will certainly get an HDMI DVI adapter. I had a similiar problem as you in regards to the boot loop. If you haven't already done so, when you get to the boot screen, type in -v cpus=1. I have seen people say to type in cpus=1 but not the combination I just provided. I was able to load iPC just fine. Problem that I am having now is determining the appropriate things to install. Per wiki (http://wiki.osx86project.org/wiki/in...0.5.6/Desktops) the following should be installed for a Studi 540 using iPC:

Dell Studio 540

• iPC 10.5.6 Universal Final
• Kernel: 9.5.0 voodoo
• Chipset: LegacyAppleIntelPIIATA
• Audio: Azalia Audio Package
• CPUS=1 boot flag fix
• LAN: Realtek R1000 Driver

You will need to do a "CPUS=1" boot flag in order to boot the install disk depending on which processor you have.
This computer had a Nvidia 9500 GT Graphics card, not the built in video. I am not sure what is needed for the built-in video chipset.
This guide was written using a Studio 540: OSX Leopard 10.5.6 Installation Guide For Complete Beginners

Here is the problem, they don't use the onboard video card (HDMI, I am not talking about the VGA). Hopefully what I provided helped and I can use your results assuming you acheive success. Please update us.