I have the e1705. It's freakin awesome. But I don't have the gpu... I have the gma945... but with the 7900 I'm sure it'll be a beast. It looks like you are gonna be using this for gaming and photoshop (looking at the specs)... so why do you care about battery life? (just get an extra adapter haha) When my e1705 was new I was getting around 4-5 hours of battery life... now it's about 3 hours (regular stock battery). But yours w/ the 7900... I heard from others that they only get about 2 hours with the 7900. I recommend the e1705... and your specs are hella better than mine.
I have core duo 1.83ghz 512mb 667mhz MSxp gma945 and everything else... and it still plays FEAR and Doom3 haha, but I'm not an intense gamer so low resolution works for me. I'll leave the high resolution up to my desktop.