Inspiron 530s, BIOS flash to utilize Quad Core CPU's?

There is no difference in the BIOS for the M02 VS M03.  530S models DO NOT HAVE a 350w power supply option.  Request denied.  There is no way to do what you are asking.  Putting a quad into an M02 version of the board will permanently damage the voltage regulators on the board and KILL the board and the power supply.

FoxConn Dell P/N FM586 / G33M03 motherboard, with a 350w PSU allows Quad Core processors.

G679R, RY007, CU409, RN474, K216C, GN723, G33M02 do not work with QUADS.

Prior to installing the processor you must have BIOS Version 1.0.15, or higher installed and the optional  PS-6351-2 350W (K661T, K660T, J515T, J517T, U343D, U342D, G738T)power supply.

These are the best Dual Core validated -
N654J Wolfdale Dual Core Kit, E8600, 3.33GHz, 6MB, 1333FSB, 65W, E0
D923J Wolfdale Dual Core Kit, E8500, 3.16GHz, 6MB, 1333FSB, 65W, E0

The reason the G33M02 doesn't support Core 2 Quad processors is because it only has 6 voltage regulator ICs, the DG33M03 has 11.

The following processors are compatible:

Intel Pentium Dual-Core 2140 (1.6 GHz, 800 MHz FSB)
Intel Pentium Dual-Core 2160 (1.8 GHz, 800 MHz FSB)
Intel Pentium Dual-Core E5200(2.5 GHz, 800 MHz FSB)
Intel Core 2 Duo E4300 (1.8 GHz, 800 MHz FSB)
Intel Core 2 Duo E4400 (2.0 GHz, 800 MHz FSB)
Wolfdale Core 2 Duo, E5200, 2.5GHz, 2MB, 65W, M0
Intel Core 2 Duo E6320 (1.86 GHz, 1066 MHz FSB) 65nm
Intel Core 2 Duo E6420 (2.13 GHz, 1066 MHz FSB)
Intel Core 2 Duo E6550 (2.33 GHz, 1333 MHz FSB)
Intel Core 2 Duo E6750 (2.66 GHz, 1333 MHz FSB)
Intel Core 2 Duo E7400 (2.80 GHz, 1066 MHz FSB)
Wolfdale Core 2 Duo, E8400, 3.0GHz, 6MB, 1333FSB, 65W, E0 45nm
Wolfdale Core 2 Duo, E8500, 3.16GHz, 6MB, 1333FSB, 65W, C0
Wolfdale Core 2 Duo, E8600, 3.33GHz, 6MB, 1333FSB, 65W, E0
Yorkfield Quad Core, QX9300, 2.5G, 6MB, 1333 FSB
Yorkfield Quad Core, Q9450, 2.66G, 12MB, 1333 FSB
Yorkfield Quad Core, Q9550, 2.83G, 12MB, 1333 FSB
Yorkfield Quad Core, Q8200, 2.33G, 4MB, 1333 FSB
Yorkfield Quad Core, Q9550, 2.83G, 12MB, 1333 FSB
Yorkfield Quad Core, Q8300, 2.5G, 4MB, 95W
Yorkfield Quad Core, Q9400, 2.66G, 6MB, 1333 FSB
Yorkfield Quad Core, Q9650, 3.0G, 12MB, 1333 FSB
Kentsfield Quad Core, Q6600, 2.4G, 8MB, 1066 FSB

Conroe E6850, 3.0G, 4MB, 1333FSB, G0
Conroe E6700, 2.66G, 4MB, 1066FSB, B2
Conroe E6600, 2.4G, 4MB, 1066FSB, B2
Wolfdale E5700 3.0GHz 65W Dual-Core

Largest upgrade > Intel Core 2 Quad Q9650 (3.0GHz, 1333 MHz FSB)

It most definitely won't kill the power supply. That's not how that works. The Core 2 Quad q8400, under load, uses approximately 165w of continuous power. The E6750 that is currently in the board utilizes 125w of continuous power under load. The current power supply is rated at 250w. The highest power graphics card I have in there utilizes about 20w under load, and I've stress tested a 35w graphics card as well, without any issue. The issue is NOT the VRM, because those have no impact on whether or not the power supply will somehow feedback loop into itself and die. The VRM are there to control voltages to maintain clock speeds, which prevents crashes and instability in the operating system. 

you are correct