But it's only for office work. I doubt onboard would suck up that much. If you were trying to game with onboard graphics, then there's an issue.
If your going with your original idea, I don't know if I'd bother getting a Core 2 Duo. Those boards only support 800FSB, and are quite old so it may not even boot up with a C2D.
The Gigabyte board definitely does not support any dual core CPU. As seen here:
GIGABYTE - Support - Motherboard - CPU Support List
The ASRock sounds like it would work though assuming you got PCB Version R2.00 and BIOS P2.80:
- LGA 775 for Intel® Core™ 2 Extreme* / Core™ 2 Duo* / Pentium® XE / Pentium® D / Pentium® 4 / Celeron® D, supporting Quad Core Kentsfield processors
- FSB 1066** MHz for external graphics (by overclocking)
- FSB 800/533 MHz for internal graphics
- Supports Hyper-Threading Technology
- Supports Untied Overclocking Technology
- Supports EM64T CPU
*Only supported with PCB version R2.00 or higher, and BIOS P2.80 or higher.
**FSB1066-CPU is supported by overclocking only when you adopt an external VGA card and DDR400 CL2.5 memory modules.
I still think your better off buying something that use DDR2 and has true, proper support for C2D. It's a whole $50 more about to get it all new, as that's how much 1GB DDR2 RAM costs. This way it makes future upgrades really easy, such as dropping in another 1GB of RAM since DDR2 is so cheap these days (DDR is not). I guess it depends how much money you have...