The best gaming laptop ?

Well, first I think this will simplify your decision, "These are the exact same notebook."

Alienware puts a different top of theirs that's it.

If you look closely at Alienware's site you will see the Soundblaster Audigy 2 is a PCMCIA card, it is not built in. I can give you the same thing, add $95.

The tv tuner is an additional option you can get on the system, and yes, you can hook it up to external speakers which would be best with the Soundblaster card because you wouldn't have to constantly hook and unhook them from the notebook (just pull out the card).

The battery is going to last the exact same.

The memory running at 333 compared to 400, you will notice a speed difference favoring the RAM I use because the timings on my modules are equivalent to the fastest desktop overclocking RAM... 2-2-2-5. I actually offer a downgrade to DDR400 CAS 2.5, but the timings are 2.5-4-4-8 (same as Alienware's).

You're somewhere close to $3,999 shipped for the tv tuner and the Audigy card with me... that's a rough estimate off the top of my bean.
That configuration is:
ML-44 2.4 Ghz
2 Gigs 2-2-2-5 timing Ultra Low Latency DR333
100 Gig 7,200 rpm Hard Drive
802.11 b/g/G+ 108 Mbps internal wireless
Soundblaster Audigy ZS2 PCMCIA
tv tuner

The same system through Alienware is: $4893 + $127 shipping (I am not kidding, that is right off their site) OVER 5 grand!

Now Alienware offers these extra carnival trinkets that I don't...

Alienware® Ozma 7™ Headphones with S-Logic™ Technology - Included!
Alienware® Aurora mALX Exclusive Hand-Airbrushed Finish by Smooth Creations - Included!
Alienware® Exclusive AlienGUIse Theme Manager – Included!
Alienware® ALX Aurora mALX Backpack - Included!
Alienware® ALX Custom Name Plate - Included!
Alienware® ALX Felt Cloth Protector - Included! Wow!
Alienware® ALX Keychain - Included!
Alienware® ALX Luggage Tag - Included!
Alienware® ALX Mousepad - Included!
Alienware® ALX Pen - Included!
Alienware® ALX Portfolio - Included!
Alienware® ALX Polo Shirt

I think I can live without a keychain, pen and a piece of felt since they are $1,000 more. Instead of the Alienware luggage tag, get the K/N and actually go to the islands with the money you save!
For $250 more you can upgrade to the Killer Notebooks "select few" package which includes:
*Your own Killer Notebooks email*Cold Steel Tai Pan Dagger Etched with the Killer Notebooks seal and your name incase of attempted Alien Abduction...
And the LORD said in a tongue unknown to man so that the aliens understood, "Therefore whosoever slayeth the bearer of this seal, vengeance shall be taken on him sevenfold and seventy." So you've got that going for you.

KillerNotebook builds a LOT of custom laptops, so if you make the request, I'm sure he can build one for you w/out OS pre loaded.
Believe me, I'm looking into KN as well 8)

The more product the better.