360j vs 740 vs 725

[Squirrel]

Currently Im looking at laptops and one of the best options for my price range ($1800 or less canadian) and performance needs is the Asus z71.
-I travel around between 2 residences and school
-enough power to play doom 3 engine
-weight and heat to sit on my lap
-and 3 hours of battery life for note taking lectures

Asus Z71 Specs (minus chip):
Chipset: Intel 915GM & ICH6
GPU: nVidia GeForce Go 6600 128MB PCI-E X16.915PM
Ram: 2x Kingston 512MB DDR2 533Mhz
HD: Fujitsu 80GB 5400rpm 8MB Cache SATA
Optical: 8x DVD & 24x CD-RW Combo Drive
Wireless: Intel 802.11 A/B/G
Monitor: 15.4" WSXGA (1680x1050) TFT Display
store with custimizing options: http://www.lucomputers.com/aStore/default.asp?systemid=48&showcase=1

While researching some of the components going into it, I came across a startaling find http://www.overclockers.com/articles1230/index05.asp that when you simply flip the switch in the system you get a no hassle OC on a stock laptop with the intel chips clocked at 400mhz.

what is the best option:
360j seems to have the best price/performance getting stock 750 results for $200 less

1. is the loss of cache a big problem for gaming?
2. are the power saving features really that key?
3. does the 360 support sata and ddr2 (i think it is MoBo dependent, which is the 915 in this case, but just wanted to check)?

Other than that the 725 is actually more expensive than the 740 around here, but it gets a big performance upgrade with this mod so i can justify it, but would rather take the 360j if i could get away with it, cause its savings of $150+

Thanks,
Squirrel