$4 for 2x1G is a good deal. Crucial Ballistix is very good for overclocking. I use them.
I hope the Dell mobo BIOS can recognize the faster ram sticks, even if it doesn't run beyond 800MHz. Some really crappy mobo won't even recognize the faster ddr2 sticks and won't even boot.
In your case, hey it's just $4AR. You can at least sell them for $10 on fleabay :)