Help finalizing M6400 purchase

I have about a $4k budget for a new laptop. I'm looking at the M6400 models and want some help finalizing my purchase.

Is there any difference between the Covet and the standard M6400? It seems that both can be configured to be essentially the same machine (besides color).

Assuming no other difference it seems that I can get a much better deal buying the standard M6400, with the RAM and HDD stripped down to the minimum and buying those aftermarket. Unless I'm missing some reason why this would be a bad idea.

So, this is what I'm thinking of doing:

Non-Covet M6400
T9550 CPU
Vista Business 64-Bit
LED E2E display
FX3700M GPU
1GB RAM
Integrated webcam (required with display)
80GB 5400 HDD
DVD +/- RW
1510 Wireless card

Everything else is default.

The total comes in at $3,549.

Now, if I buy 4x2GB DDR3 1066 RAM modules aftermarket I can get them for around $160.

I could add a couple of 320GB HDD's for another $160.

That brings the total up to $3,869.

Is there any problems with the RAM or HDD that I am choosing? Is there any reason to go with the Dell OEM stuff as opposed to the aftermarket? If I configure the laptop the same way at Dell it comes in at $4,778. Seems like I can save almost a grand doing it this way and stay inside my budget.

About the only things that I can see different is that the Dell HDD's have a free fall sensor. Not sure if that's something that comes on aftermarket drives or not, or if it really is that important.

It is also confusing because on Dell's website there is a banner above the HDD's that says "Fast & Reliable - 10,000RPM SATA Hard Drive", yet I see no option for a 10,000 RPM HDD listed.

So, comments/suggestions on this strategy? Thanks!